calibration services brochure

MIKES METROLOGY Calibration Service

International competitiveness and reliability

2 — VTT MIKES METROLOGY Calibration services

Copyright © VTT MIKES 2016

Teknologian tutkimuskeskus VTT OyPL 1000 (Vuorimiehentie 3, Espoo), 02044 VTTPuh. +358 20 722 111, faksi +358 722 7001www.vttresearch.com

VTT MIKES METROLOGY Calibration services 2016 — 3

VTT MIKES - metrology

Mass, pressure, flowCalibration of weights ................................................................................... 6Calibration of pressure measuring devices ................................................. 8Calibration of force and torque .................................................................. 10Water flow meter calibrations ..................................................................... 12Calibration of gas flows and density of liquids ........................................... 14Acceleration of free fall .............................................................................. 16

Temperature, humidityCalibration of hygrometers ......................................................................... 18Calibration of radiation thermometers ....................................................... 20Fixed point calibration of platinum resistance thermometrs ...................... 22

Electricity, acousticsCalibration of direct voltage and current ................................................... 24Calibration of alternating voltage ............................................................... 26Calibration of capacitance and inductance standards ............................... 28Calibration of resistance ............................................................................ 30Calibration of power and energy at line frequency .................................... 32RF- and microwave calibrations ................................................................ 34High voltage and high current .................................................................... 36Acoustic calibrations .................................................................................. 38

TimeCalibration of time, time interval,and frequency ........................................ 40

OpticsOptical quantities ........................................................................................ 42

Length, geometryQuantitative Microscopy - Atomic force microscope .................................. 44Characterization of nanoparticles .............................................................. 46Calibration of laser interferometers ............................................................ 48Interferometrical calibration of gauge blocks ............................................. 50Calibration of gauge blocks by mechanical comparison ........................... 522D- and 3D-measurements of form and surface roughness ..................... 54Optical measurements of surface microstructures .................................... 56Calibration of tachymeters ......................................................................... 58Angle and perpendicularity measurements ............................................... 60Measurements of accurate inner and outer dimensions ........................... 62Coordinate measurements ........................................................................ 64Optical coordinate measuring - vision measuring ..................................... 66Calibration of line scales and distance meters .......................................... 68Interferometric measurements of flatness and form .................................. 70Machine tools measurements .................................................................... 72Measurements of roundness ....................................................... ..............74Calibration of microscopes and calibration standards ............................... 76Length in geodesy ...................................................................................... 78Water quality .............................................................................................. 80

4 — VTT MIKES METROLOGY C alibration services 2016

VTT MIKES - metrologyMIKES Tekniikantie 1 02150 ESPOO

MIKES-Kajaani Tehdakatu 15, Puristamo 9P19 87100 KAJAANI

Tel. +358 020 722 111 (call center) Email: [email protected]

Finland has a slightly distributed metrology infrastructure. MIKES is the National Metrology Institute and it acts as the National Standards Laboratory for most of the quantities. MIKES designates the other National Standards Laboratories and Contract Laboratories..

• We realize SI-system of units in Finland• We do high level research in the field of

metrology• We develop measurement methods for

industry and society• We offer high level calibration servive, expert

service and training

MIKES is a specialised research institute for measurement science and technology. As the National Metrology Institute of Finland, MIKES is responsible for the implementation anddevelopment of the national measurement standards system and realisation of the SI units in Finland.

The number of staff is 65 supported by VTT Ltd. administration.

The MIKES building is situated in the city of Espoo and its branch office in Kajaani is the northernmost National Stan-dards Laboratory in the world. The high-quality laboratories provide the most accurate measurements and calibrations – close to 1600 certificates per year – in Finland.

MIKES also performs high-level metrological research and develops measuring applications in partnership with industry. The activities of MIKES aim to improve industrial competitive-ness, the national innovative environment, and public safety.

MIKES is a signatory to CIPM MRA (International Committee for Weights and Measures, Mutual Recognition Arrangement) and a member of EURAMET (European Association of Natio-nal Metrology Institutes). Through international collaboration, MIKES is linked to the international measurement system and to the European and international metrology research com-munity. MIKES takes actively part in the European Metrology Research Programme (EMRP and EMPIR).


Figure 2. CIPM MRA -logo tells us, that our measure-ment results are accepted globally.

Acoustics: 30Length: 59Time and frequency: 11Thermometry: 44Optics: 53Mass and related quantities: 28Electricity: 99Ionising radiation: 30Chemistry: 5

Total Finland: 359 / total 24031 entries.Source: BIPM, July 1, 2015, kcdb.bipm.org

Voluntary peer review project

MIKES is a coordinator in the EURAMET TC-Q project Peer reviews of Quality Management Systems (QMSs). The ot-her partners in the project are CMI (CZ), GUM (PL) and SMU (SK). The project supports the evaluation and imp-rovement of QMS processes and procedures of the parti-cipating institutes. Learning from each other and sharing the best practice for QMS implementation are other goals of the project. The QMSs of the institutes are based on ISO/IEC 17025. A programme with on-site visits by peers is planned on an annual basis and one or twofields in each institute are reviewed every year. In 2012, the QMS of MI-KES in the field of length metrology was peer reviewed by an expert from GUM, and vice versa. Also the humidity la-boratory of MIKES was peer reviewed by a GUM expert.

Calibration and MeasurementCapa-bilities (CMCs)recorded in the BIPM keycomparison database,KCDB

Electricity, acoustics, time, frequency, temperature, humidity, pressure, mass, force, torque, flow and length

Water quality Air quality Ionising radiation Length in geodesy and acceleration of free fall

The National Measurement Standards System

Figure 1. National measurement standards system in Finland. MIKES=VTT MIKES Metrology, Aalto=MIKES Aalto Metrology Insitute, SYKE=Finnish Environment Institute, FMI=Finnish Meterological Institute, STUK=Radiation and Nuclear Safety Authority and FGI=-Finnish Geospatial Research Institute.

Photometry and radiometry

The Metre Convention

6 — VTT MIKES METROLOGY Calibration services 2016

Mass, pressure flow

Temperature humidity

Electricity, time acoustics Optics Length

geometry Chemistry

Calibration of weightsMIKES, Tekniikantie 1, 02150 EspooMIKES-Kajaani, Tehdaskatu 15, 87100 Kajaani, Tel. +358 20 722 111.

Maija Ojanen-Saloranta, Senior Research Scientist, Tel. +358 50 443 4214 (Espoo)[email protected]

Kari Kyllönen, Research Techni-cian Tel +358 50 4434180 (Kajaani), [email protected]

Traceability

The weight standards of MIKES mass laboratory are traceable via the Pt-Ir prototype number 23 of kilogram to the internatio-nal prototype of kilogram kept at the BIPM. The comparability of measurement standards of mass laboratory is maintained by international comparisons (e.g. EURAMET key compa-risons). We carry out research and development related to scales and weights and offer expert services on the usage of scales and weights. Our mass laboratories are of high quality and we have scales equipped with automatic weight handlers. Our laboratories are located in Espoo and Kajaani.

Measure methods

The measurement range of mass at MIKES is 1 mg ... 2000 kg. The calibrations of weights are performed by using gene-rally acceptedweighing methods: the direct comparison method and the subdivision method. In the first method, the weight is dire-ctly comparedto a standard and in the latter a set of weights is calibrated by using one or several weight standards.


Calibration of weights

Table 1. Measurement uncertainties of weight calibrations.

Calibration services MIKES is capable to calibrate weights of OIML classes E1, E2, and F1, whose nominal masses are at most 20 kg (E1), 50 kg (E2) and 2000 kg (F1). In addition, MIKES offers calibration services for weights of lower OIML classes, whose masses are between 10 kg and 2000 kg. MIKES also calibrates other weights such as weights of pressure balances. In the calibration certificate, the masses are given as conventional masses or as true masses. The smallest achievable measurement uncertainties in mass calibrations are presented in table 1. Weights whose nominal mass is 50 kg or bigger are calibrated at MIKES Kajaani.

Calibration of volume of weights

When calibrating a weight, a correction due to the air buoyancy has to be made to the weighing result. The magnitude of the correction depends on the volume of the weight and on the density of air. In order to be able to make the correction accurately enough, the volumes of the most accurate weights have to be known. Mass laboratory calibrates volumes and densities of solid artefacts. The density standard is either distilled water or silicon. The measurement methods is hydrostatic weighing. The measuring equipment is suitable for volume calibration of 2-kg weights or lighter. If needed, volumes of bigger weights can be determined by using e.g. dimensional measurements. The measurement uncertainties of volume calibrations of weights are presented in table 2.

Table 2. Measurement uncertainties of calibrations of weight volumes.

*) Calibration in MIKES-Kajaani

Mass Measurement uncertainty (k=2)

2000 kg *) 3000 mg

1000 kg *) 1500 mg

500 kg *) 750 mg

200 kg *) 300 mg

100 kg *) 200 mg

50 kg *) 30 mg

20 kg 3.0 mg

10 kg 1.5 mg

5 kg 1.0 mg

2 kg 0.3 mg

1 kg 0.05 mg

500 g 0.03 mg

200 g 0.02 mg

100 g 0.015 mg

50 g 0.010 mg

20 g 0.008 mg

10 g 0.007 mg

5 g 0.005 mg

2 g 0.004 mg

1 g 0.003 mg

500 mg 0.003 mg

200 mg 0.002 mg

100 mg 0.0015 mg

50 mg 0.0015 mg

20 mg 0.0010 mg

10 mg 0.0008 mg

5 mg 0.0008 mg

2 mg 0.0008 mg

1 mg 0.0008 mg

Mass Volume Uncertainty (k=2)1 g – 2 kg 0.1 – 255 cm3 0.000 3 – 0.008 cm3


Mass, pressure flow



geometry Chemistry

Calibration of pressuremeasuring devices

MIKES, Tekniikantie 1, 02150 Espoo Tel +358 20 722 111 www.mikes.fi

Monika Lecklin, Research techni-cian, Tel. +358 50 410 [email protected]

MIKES has good capabilities to calibrate different measuring devices of pressure. The measuring range for gauge pressure is 0 ... 500 MPa and for absolute pressure 0.0005 Pa ... 1.75 MPa. The best measurement

standards at MIKES are pressure balances, which are used to realise pressure according to its definition p = F / A, i.e. pressure is force divided by area. The force is produced by the mass of the piston of the pressure balance and by the masses of weights loaded over the piston. The local value for the acceleration of free fall must be known. The area A is the effective area of the piston cylinder assembly of the pressure balance. Pressure balances are used for gauge and negative gauge pressure measurements and for absolute pres-sure measurements. To cover a wide range of pres-sures, several piston cylinder assemblies of different sizes are needed in order to be able to realise diffe-rent pressures and to keep the number of weights still easy to handle. In pressure ranges below the range of pressure balances, capacitive sensors and spinning rotor gauges are used as measurement standards. The lowest pressures (absolute pressures 0.0005 Pa ... 2 Pa) are calibrated by using spinning rotor gauges. These measurements are demanding as they require long stabilisation and measurement times. Measure-ment methods and devices used for pressure depend on the pressure range.

Figure 2. Pressure measurements are made in a very broad pressure range, for instance from 10-9 Pascals required in particle accelerators to over 109 Pascals, i.e. 1 GPa, pressures used in powder met-allurgy. Measuring devices and their operational principles are very different in different pressure ranges. The measurement range in MIKES is from 0.5mPa to 500 MPa and is marked with blue bar in the figure.

Figure 1. Pressure balance is used for the traceable rea-lization of pressure unit.

Sari Saxholm, Senior Research Scientist, Tel +358 50 410 5499, [email protected]


Calibration of pressure

Absolute pressureThe ideal vacuum as reference point (vacuum gauges).

Atmospheric pressureAtmospheric pressure is the absolute pressure cau-sed by the atmosphere so the reference is the ideal vacuum (barometers).

Figure 3. In practice, measurement of pressure is always measu-ring differential pressure. Depending on the reference point various names are used for pressure and diverse devices used.

Negative gauge pres-sure gaseous mediumPressure range (Pa)

Relative measurementuncertaintyk = 2 (%)

Gauge pressurein oil medium

Pressure range (Pa)


-100 0.03 500 000 (0,5 MPa) 0.005

-1000 0.01 1 000 000 (1 MPa) 0.004

-10 000 0.005 10 000 000 (10 MPa) 0.003

-100 000 (-0.1 MPa) 0.004 100 000 000 (100 MPa) 0.003

500 000 000 (500 MPa) 0.01

Figure 4. Piston cylinder assemb-lies of different size for pressure balances.

Absolute pressuregaseous medium

Pressure range (Pa)


Gauge pressuregaseous medium

Pressure range (Pa)


0.0005 9 100 0.03

0.001 6 1000 0.01

0.01 3 10 000 0.004

0,. 3 100 000 (0.1 MPa) 0.003

1 2 1 000 000 (1 MPa) 0.002

10 0.5 10 000 000 (10 MPa) 0.004

100 0.1 16 000 000 (16 MPa) 0.004

1000 0.01

10 000 0.005

100 000 (0,1 MPa) 0.004

1 000 000 (1 MPa) 0.004

1 750 000 (1.75 MPa) 0.003

Gauge pressureThe reference point is the atmospheric pressure. E.g., the tyre pressure of a car is gauge pressure. Any gauge pressure can be converted to an absolute pressure by adding the momentary atmospheric pressure

Negative gauge pressureThe reference point is the atmospheric pressure. When converted to absolute pressures, negative gauge pres-sure is thereby lower than the atmospheric pressure. Thus, negative gauge pressure means that the objects pressure is lower than the pressure in its environment.

Differential pressurePressure is called as differential pressure especially when the reference pressure is other than the vacuum or the atmospheric pressure. The reference pressure is then usually called asa line pressure.

Absolute pressure

Differential pressure

Absolut pressure

P=0

Atmospheric pressure

Gauge pressure


Mass, pressure flow



geometry Chemistry

Calibration of forceand torque

MIKES, Tehdaskatu 15, Puristamo 9P19, 87100 Kajaani, Tel. +358 50 443 4213 www.mikes.fi

Sauli Kilponen, Research Engi-neer, Tel. +358 50 443 [email protected]

Jani Korhonen, Research Engi-neer Tel. +35850 443 [email protected]

Traceability andcalibration of forceVTT MIKES-Kajaani performs force calibrations from 1 N to 1.1 MN. Calibrated measurement devices are usually force transducers, force measurement de-vices, balances (eg. hook, wheel weight and airplane) and pull force testers. The smallest measurement un-certainty is 2×10-5. The calibration of force is based on the ISO 376 stan-dard. The force calibration from 1 N to 110 kN is car-ried out in dead weight force standard machines. A dead weight machine is a mechanical structure that generates force by subjecting dead weights to the lo-cal gravitational field. Hydraulic force standard can be used in the calibrations from 20 kN to 1.1 MN. The masses that are used in VTT MIKES-Kajaani are traceable to the national standard of mass, which is in turn traceable to the international prototype of the kilogram held in the BIPM. Force traceability is reali-sed from mass calibrations and international compa-risons.

Figure 1. A 1-MN hydraulic force standard and a 100-kN:n direct load force standard. The total height of the equip-ment is eight meters, including the load masses below floor level.

Load method Measurement range Measurement uncertainty (k=2)

Direct load Compression/pulling: 10 nm ... 10 kN 2 . 10-5 Direct load Compression/pulling: 10 kN ... 100 kN 5 . 10-5

Hydraulic load Compression/pulling: 20 kN ... 1 MN 1 . 10-4 Field calibration of force 1 N ... 1 MN 5 10-4

Table 1. Measurement ranges for force.


Calibration of force and torque

Torque standard Measurement range Measurement uncertainty (k=2)

Lever – mass 0.1 ... 10 Nm right/left 5 . 10-4

Lever – mass 10 ... 2000 Nm right/left 5 . 10-4

Reference standard 2 ... 20 kNm right/left 5 . 10-4

Traceability andcalibration of torqueMIKES-Kajaani performs calibrations of torque in the range 0.1 Nm ... 20 kNm, the smallest uncertainty being 5×10–4. The calibration of torque is carried out using reference standards for torque or standards based on reference sensors.

The need for torque calibrations can be classified in three groups of different types of devices. The most stringent accuracy requirement (< 0.05 % ... 0.5 %) is for calibration of torque sensors that are used e.g. in measurement of torque in research of rotating machines such as pumps and motors. The second group is devices used for calibration of torque-controlled assembly tools. In calibration of these devices, the uncertainty of the torque standard should not exceed 0.5 %. The third group is calibration of torque-controlled assembly tools for industries that do not have their own calibration devices. The calibration uncertainty for torque-controlled assembly tools is typically from 1 % to 10 %.

There exist only a few standards for torque cali-brations. For torque-controlled assembly tools is the standard ISO 6789, which however mainly describes test methods but also defines a cali-bration procedure. There is no standard for devices used for calibration of torquecontrolled assembly tools. For torque sensors there exists the recommendation Euramet/cg-14.

Figure 2. A 2-kNm torque standard used for comparison measurements in the range 100 Nm – 2 kNm and for calibration of torque sensors.

Torque is a derived quantity that consists of known masses and a known length of a lever arm. Even though traceability for masses and length can be achieved separately, verifying the consistency of torque in entity is mainly verifying the consistency of torque in entity is mainly based on interlabora-tory comparisons

Figure 3. A 20-kNm torque standard based on a reference sensor.

Table 2. Measurement ranges for torque.


Mass, pressure flow



geometry Chemistry

Water flowmeter calibrations

MIKES, Tehdaskatu 15, Puristamo 9P19, 87100 Kajaani,Tel. +358 50 443 4213

Mika Huovinen, Researcher, Tel. +358 50 415 [email protected]

Timo Nissilä, Research Engineer, Tel. +358 50 443 4175 [email protected]

Calibration providesreliabilityAccurate liquid flow measurements are needed in many areas of industry, such as process, mining and energy industry. To maintain global competitiveness and high quality of the end products, accurate liquid flow measurements make it possible to optimise dif-ferent industrial processes and in this way reduce raw material consumption and emissions to environment. Regular calibration and stability tracking of liquid flow meters are essential part of measurement reliability, regardless of the application. Figure 1. Graphical user interface of the D200

liquid flow calibration rig.


Water flow meter calibrations

TraceabilityThe most important activities of MIKES Kajaani are to implement the traceability of the flow measurements in Finland, maintain liquid flow measurement standards, and provide calibration and expert services. These are achieved by participating in international and domestic research and intercomparisons projects. The MIKES’s liquid flow calibration laboratory’s quality management system is based on the ISO/IEC 17025 standard.

Calibration servicesMIKES Kajaani has three different calibration rigs for liquid flow calibrations. One of the rigs is the national measurement standard of flow. In this rig, the measu-ring principle is gravimetric and the measurements carried out are traceable to the national standards of mass, temperature and time.

The gravimetric reference standard of water flow is ba-sed on weighing the water. In the measurements, wa-

Table 1. Measuring ranges of the liquid flow calibration rigs and the measurement uncertainty.

ter is first continuously pumped up to a constant head tank located 20 m above ground level. The water le-vel is held constant in the tank by sufficient overflow and by adjusting the water flow in a measuring pipe section, where the flow meters under test are placed. The calibration is done by comparing the results of the balance and the meter under test reading.

In the closed loop type calibration rigs, the referen-cemeters are usually magnetic or coriolis mass flow meters. In these rigs, the source of traceaility up to DN200 is based on the national flow standard. For pipe sizes DN200 > , the source of traceability is a foreign NMI, typically PTB from Germany.

The measuring principles, ranges, and reachablemeasurement uncertainties are shown in Table 1.

For pulp and paper industry, MIKES Kajaani has a mass circulating rig applied with a cooling system. Consis-tency area 0 – 12 % and flow speed 0.5 – 3 m/s.

Equipment Measuringprinciple

Pipe sizes Volume flow Pressure Measurement uncer-tainty(k=2)

D100 referencemeter

DN 15DN 50

0.3…20 L/s <0.7 MPa 0.3 %

D500 referencemeter

DN 150DN 500

7… 750 L/s <0.5 MPa 0.3 %

D200 gravimetric DN 10DN 50DN 100DN 200

0.1 l/s… 200 L/s 0.2 MPa 0.03 %

Figure 2. Part of the D500 liquid flow calibration rig.


Mass, pressure flow



geometry Chemistry

Calibration of gas flowsand density of liquids

MIKES, Tekniikantie 1, 02150 Espoo Puh. 020 722 111 www.mikes.fi

Richard Högström, Senior Research Scientist, Tel +358 50 303 [email protected]

Heikki Kajastie, Researcher, Tel +358 50 410 [email protected]

Martti Heinonen, Principal Metrologist, Tel. +358 400 686 553, [email protected]

Calibration givesreliabilityNowadays, measurement of small gas flows is nee-ded in various applications. For instance, in health care and medical industry is very impor-tant to as-sure the safety of customers. In order to maintain in-ternational competiveness and to guarantee the high quality of products, the accuracy of gas flow measu-rements in process industry has to be reliably veri-fied. No matter what the application is, the regular calibration and stability monitoring of gas flowmeters is an essential part of quality control. MIKES cali-bra-tes gas flowmeters in the flow range 5 ml/min...110 l/min and offers research and expert services in the field of gas flow meas-urements and their reliability

TraceabilityMIKES provides circumstances for traceable gas flow measurements in Finland by developing and maintaining standards for gas flows and offers calibration and expert services.

The traceabiltity of gas flows at MIKES is based on a dynamic weighing system, DWS developed at the flow laboratory of MIKES. The measure-ments performed using this system are traceable to the national standards of mass and time. The DWS equipment is used to calibrate measure-ment standards based on laminar flow elements (LFE) and customers’ devices whose relative ac-curacy level is better than 1 %.

The high level of our gas flow measurement ac-tivities is maintained by actively participating in international research projects and compari-sons and by carrying out own research projects in this field.


Calibration of gas flow and density of liquids

Quantity Measurement range Measurementuncertainty (k=2)

Mass flow (DWS) 0.1 mg/s...625 mg/s 0.3 %...0.8 %Mass flow (LFE) 0.1 mg/s...625 mg/s 0.4 %...0.9 %Volume flow (LFE) 5 ml/min...30 l/min 0.4 %...0.9 %

Density of liquid (LDCS)

600 kg/m3...2000 kg/m3 15 ppm

Calibration ofareometers (HCS)

600 kg/m3...2000 kg/m3 0.05 %

DWS = Dynamic weighing systemLFE = Laminar flow elementLDCS = Liquid density calibration systemHCS = Hydrometer calibration system

Calibration servicesIf the relative accuracy level of a gas flowmeter is better than 1 %, the DWS equipment will be used in the calibration. Typical examples of such flowmeters are high-quality laminar flow elements and some pis-ton-cylinder volume flowmeters.

Most of our customers’ flowmeters are calibrated at MIKES using the LFE calibration equipment. It is much more convenient to use than the DWS equip-ment and it does not have such a strict tolerances for environmental conditions. Performing of calibra-tions are thus more flexible and faster. The equip-ment has proven to be well suited for calibration of gas flowmeters having relative accuracy above 1 %. Such meters include thermal mass flowmeters and controllers.

Furthermore, MIKES performs liquid density measu-rements. We calibrate for instance areometers and density meters based on vibra-tions and determine densities of customers own liquid samples in the density range 600 kg/m3 ... 2000 kg/m3.

Table 1. Measurement ranges and best achievable calibration uncertainties at MIKES.


Mass, pressure flow



geometry Chemistry

Acceleration of free fall

Finnish Geospatial Research Institute, FGIThe Finnish Geospatial Research Institute, FGI, of the National Land Survey of Finland maintains measu-rement standards for geodetic and photogrammetric measurements and is the National Standards La-boratory of acceleration of free fall and length. The FGI takes care of the fundamental measurements in Finnish cartography and of geographical information metrology and carries out scientific research in geo-desy, geographic information sciences, positioning, navigation, photogrammetry and remote sensing.

Methods and traceabilityThe national measurement standard is the absolute gravimeter FG5-221. Its results are directly traceable to length and time standards. We have participated in all international comparisons since the year 1989. At a customer’s site the measurements are usually perfor-med with a relative gravimeter, measuring the gravity difference with respect to a point with known gravity.

Acceleration offree fall and gravityThe acceleration of free fall depends on location and time. The time dependence originates from tidal for-ces (variation in Finland 3 μm s–2) and from mass va-riations of groundwater and atmosphere (at least an order of magnitude smaller). When the most impor-tant time variations are removed from the acceleration of free fall by using agreed methods, the result is the acceleration due to gravity, which can be treated as a time independent quantity..

Markku Poutanen, Prof.,Tel. +358 29 531 4867,[email protected]

Mirjam Bilker-Koivula,Senior research scientistTel. +358 29 531 4696 [email protected]

Hannu Ruotsalainen,Senior research scientist,Tel. +358 29 531 [email protected]

Finnish Geospatial Research Insti-tute, FGIGeodeetinrinne 2, 02430 Masala,Tel. +358 29 530 1100, www.fgi.fi

Figure 1. Acceleration of free fall in Finland, unit m s-2.


Acceleration of free fall

Figure 4. Superconducting gravimeter (Metsähovi, Kirkkonummi) registers even 0.1 nm s–2 variations in the acceleration of free fall.

Calibration services anduncertaintyWe measure gravity at requested sites and report the value for the acceleration of free fall. The time varia-tion is included in the uncertainty of 4 μm s–2 (k=2). If needed, we supply an accurate value for gravity (the smallest uncertainty is 0.008 μm s–2) and methods to predict the time variation (the smallest uncertain-ty 0.10 μm s–2). We maintain an open calibration line where customers can verify their gravimeters.

Figure 2. A measurement using a relative gravimeter.

Figure 3. The absolute gravimeter FG5X-221 is based on a free fall experiment.

Research, developmentand reportingWe carry out research and develop national infra-structure for measurements of gravity and accele-ration of free fall for all applications (e.g geodesy, geophysics and geology). With the help of the 30 000 points in the national gravity grid, the acceleration of free fall can be estimated with an accuracy of 0.1 mm s–2 without any new measurements. We have perfor-med measurements using absolute gravimeters in 20 countries.


Mass, pressure flow

Temperatue, humidity

Electricity, time, acoustic Optics Length,

geometry Chemistry

Reliability fromcalibrationReliability of humidity measurements is important, e.g. in storage of wood, paper, food, etc. in aviation and environmental monitoring as well as in diverse fields of industry and research. Cali-bration of hygro-meters at regular intervals and monitoring their stabili-ty is an essential part of verification of measurements.

MIKES provides high-quality calibration services for instruments measuring humidity of gases and expert services on research and development related to hu-midity measurements and their reliability..

Traceability to humiditymeasurements MIKES creates conditions for traceable humidity measurements in Finland by developing and main-taining measurement standards for humidity and by offering calibration and expert services.

The high quality of the humidity laboratory is maintain-ed by taking part in international research and com-parison projects and by carrying out own research projects.

Calibrationof hygrometers

Hannu Räsänen, Senior Research Technician, Tel +358 50 410 5497, [email protected]

Martti Heinonen, Pricipal Metrolo-gist, +358 400 686 553, [email protected]

MIKES, Tekniikantie 1, 02150 Espoo, Tel +358 20 722 111 www.mikes.fi

Heikki Kajastie, Researcher, Tel +358 50 410 [email protected]



Calibration of hygrometers

Quantity Measurement range Measurement uncertainty (k=2)

Dew-point temperature -80 °C ... -60 °C-60 °C ... +84 °C

0.2 °C ... 0.1 °C0.05 °C ... 0.06 °C

Relative humidity 10 %rh ... 95 %rh(-20 °C ... +85 °C)

0.1 %rh ... 1.0 %rh (generator)

Relative humidity 10 %rh ... 95 %rh(+10 °C ... +85 °C)

0.4 %rh ... 2.0 %rh (climatic chamber)

Traceability Traceability of humidity measurements is based on a dew-point temperature scale. The scale is realised by using a humidity generator, which is the national measurement standard in Finland.

The core of a dew-point generator is a saturator in which total saturation of air with respect to water or ice is reached. The dewpoint temperature of the air coming out of the generator is calculated from the sa-turator temperature and from the pressure difference between the saturator and the device under calibrati-on. When saturated air is led into the measurement chamber of the generator, the equipment is also sui-table for calibration of relative humidity sensors..

The dew-point meter under calibration is directly con-nected to the dew-point generator. In calibration of a relative humidity sensor, the sensor is placed in the measurement chamber system. The reading of the sensor is compared to the value of relative humidity that is calculated from the dew-point temperature and the air temperature inside the chamber.

Calibration services Most dew-point meters are calibrated using a dew-point generator. The measurement standards of humi-dity laboratory at MIKES cover the dew-point tempe-rature range -80 °C to +84 °C. Dew-point calibrations are also carried out as comparison calibrations in ca-librators, for instance for capacitive dew-point meters.

Most relative humidity sensors are calibrated in a cli-matic chamber. The dew-point temperature and the air temperature in the chamber are measured by using a chilled mirror hygrometer and a digital thermometer, respectively. The relative humidity is calculated from measured temperature and dew-point temperature. If the achievable uncertainty is not sufficient or the tem-perature range extends to below +10 °C, the calibra-tion is performed using a humidity generator. Relative humidity sensors are calibrated in the range 10 %rh to 95 %rh at temperatures between -20 °C and +85 °C.

In cases of other humidity quantities, calibrations are performed with the same equipment the relative hu-midity calibration systems. The values of these quan-tities are calculated from measured dew point tempe-rature, temperature, and pressure.

Figure 1. Calibration of chilled mirror hygrometers.

Table 1. Measurement ranges and best achievable calibration uncertainties at


Mass, pressure flow



geometry Chemistry

Calibration of radiationthermometersHannu Räsänen, Senior Research Technician, Tel +358 50 410 5497, [email protected]

Martti Heinonen, Principal Metrologist, Tel +358 400 686 [email protected]

MIKES, Tekniikantie 1, 02150 Espoo Tel. +358 20 722 111 www.mikes.fi

Measurement methodsBlackbody radiatiors are used in calibration of radiati-on thermometers. The operation range of MIKES ra-diators is -40 °C ... 1500 °C.

The temperature of a blackbody radiator can be measured using e.g. a temperature sensor that is em-bedded in the radiator wall. When calculating the ra-diation temperature from the measured temperature, the emissivity of the wall and bottom materials of the radiating cavity and the geometry of the blackbody ra-diator as well as the temperature gradients are taken

into account. The radiation temperature measured by a radiation thermometer is often lower than the sur-face temperature of the measured object, since the surface emissivity is usually lower than the emissivity of an ideal blackbody (the emissivity of a blackbody is 1 but the emissivity of a glossy copper surface is 0.1).

In MIKES radiation thermometers are calibrated by using either a calibrated reference pyrometer or refe-rence radiators.


Calibration of radiation thermometers

Traceability

The international temperature scale ITS-90 is reali-sed above the temperature of 962 °C with a reference pyrometer and fixed-point radiators (962 °C, 1064 °C and 1085 °C). Of these fixed-points MIKES has the first and the last one which are the freezing points of silver (figure 1) and copper. Below the tempera-ture of 962 °C, ITS-90 is realised by using resistance thermometers instead of a pyrometer. The reference equipment for radiation temperatures between –40 °C … 962 °C at MIKES are based on resistance ther-mometers calibrated according to the ITS-90..

Size-of-source-effect

The size of the radiation source (size-ofsource- effect, SSE) affects the calibration results of a radiation thermometer. A radiation thermometer detects thermal radiation also outside the black-body radiator or the object to be measured. The significance of this additional thermal radiation depends on the construction of the optics (figure 2). On demand, the size-of-source-effect is measu-red at MIKES.

Figure 2. SSE: In this example,a pyrometer detects lowertemperatures whenthe aperture of the radiatoris less than 15 mm and thetemperature of the radiatoris higher than ambient temperature.

Figure 1. A silver cell that isused in the calibration of areference pyrometer.

Vocabulatory • reference meter: measurement standard • pyrometer: radiation thermometer (infraredthermometer) • a blackbody radiator does not reflect at all radiation coming from the outside.The temperature of an object depends only from the heat energy brought to the object and hence itsradiation intensity is proportional to the temperature of the object.

Silver

Inner cover graphite

Outer cover graphite


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geometry Chemistry

Fixed point calibration of plati-num resistance thermometers

Hannu Räsänen, Senior Research Technician, Tel +358 50 410 [email protected]

Ossi Hahtela, Senior Reseach Scientist, Tel +358 50 303 9340, [email protected]

MIKES, Tekniikantie 1, 02150 Espoo Tel +358 20 722 111 www.mikes.fi

Calibration objectsand methodsStandard platinum resistance thermometers (SPRT) of good quality (i.e. stable) are calibrated at the fixed points of the ITS-90 temperature scale. A fixed point cell (Figure 1) usually contains pure metal, e.g. tin, zinc, aluminium or silver (Table 1) sealed in a crucible f purified graphite. The purity of the metal is typically ca. 99.99995 %. The graphite crucible is enclosed in a fused quartz tube.

The fixed point cell is placed in a vertical tube furnace and the temperature is slowly raised until the melting is complete. At this stage the furnace temperature is reduced to a value slightly below the melt temperature in order to start solidification. When the metal is in a su-percooled state, the thermometer to be calibrated is carefully inserted into the cell. The thermometer is coupled to a resistance bridge using four wire coup-ling. The solidification state can be maintained up to 10 hours (Figure 2) and the temperature of the fixed point cell stays within ±0.5 mK.

The resistance bridge is used to measure the electri-cal resistance of the thermometer during the solidifi-cation state. The thermometers are usually calibrated using three or five different fixed points.

Figure 1. Pt25-sensor (SPRT) in a fixed point cell.


Fixed point calibration of platinum resistance thermometers

Calculation ofcalibration coefficientsThe temperature T90 is determined according to the ITS-90 temperature scale. First a resistance ratio W(T90) = R(T90) / R(T0.01°C) is calculated by divi-ding the sensor resistance at a given fixed point by the resistance value at the water triple point. A deviation function of the resistance ratio and calibration cons-tants (a, b, …) are de-termined for each sensor under calibration. The deviation function can be e.g.

W(T90) - Wr(T90) = a[W(T90) - 1] + b[W(T90)-1]2

where Wr(T90) is a reference function given in the ITS-90 scale. The deviation function to be used and the number of calibration constants depend on the temperature range and the used fixed points.

The deviation function can also be used to determine any temperature between the fixed points when the constants a and b are known. In this case, W(T90) is first determined at the unknown temperature and the resulting Wr is used to calculate T90.

Uncertainties in fixedpoint calibration The uncertainties of the fixed points at MIKES are between 0.0002 ... 0.010 °C. The lower limit is reached at the triple point of water and the upper limit at the fixed points of aluminium and silver. The uncertainty of the resistance thermometer calibrations is larger since it includes also un-certainties of the calibration equipment (resis-tance bridge, reference resistor) and the stability of the thermometer during the calibration.

Other fixed pointcalibrationsNoble metal thermocouples of B-, R- and Stype are also calibrated at fixed points. The highest fixed point temperature is the freezing point of copper at 1084.62 °C.

Figure 2. Freezing curve of zinc.

Substance Temperature (°C) State *Argon (Ar) -189.3442 tElohopea (Hg) -38.8344 tVesi (H2O) 0.01 tGallium (Ga) 29.7646 mIndium (In) 156.5985 fTina (Sn) 231.928 fSinkki (Zn) 419.527 fAlumiini (Al) 660.323 fHopea (Ag) 961.78 f* t = triple point, m = melting point,f = freezing point

Abbreviations:Pt25 = 25-ohm platinum resistance thermometer HTPRT = high temperature platinum resistance thermometer

Table 1. MIKES fixed points for resistance thermo-meters

TraceabilityThe MIKES fixed points are part of the realisation of the international ITS-90 temperature scale. The sta-bility of the fixed point cells are monitored and the temperatures they provide are compared to the tem-peratures from similar cells at our own and foreign laboratories.


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Electricity time acoustics Optics Length, geometry Chemistry

Calibration of directvoltage and current


Pekka Immonen, Researcher, Tel +358 50 410 [email protected]

Risto Rajala, Researcher, Tel +358 50 721 8397, [email protected]

Accuracy of almost all electrical measuringinstru-ments is based on traceability of direct voltage and resistance. MIKES maintains thenational standard of direct voltage and direct current in Finland. The unit of direct voltage, volt, is determined very accurately (repeatability even 10–10) by using Josephson voltage standard. The volt is transferred from the Josephson standard to Zener working standards and further to calibrators and multimeters. The measurement range is extended above 10 V by using resisive voltage di-viders. In practice traceability of direct current comes from voltage and resistance using Ohm’s law. Tracea-bility of currents smaller than 100 pA can be realized also by charging a capacitor by a linearly increasing voltage. One research topic is the development of a quantum standard for direct current based on single- electron phenomena in nanostructures.

The methods and measuring instruments developed at MIKES are of high international level. One de-monstration of this is the excellent success in interna-tional comparison measurements with other national metrology institutes. Moreover, MIKES research on direct current metrology is in the international front line. Most important research topics are development of voltage standards based on microelectrome-chani-cal systems (MEMS) and closing the so-called quan-tum metrological triangle to prove by Ohm’s law that there is a mutual agreement between the quantum standards of electric current, voltage, and resistance..

Figure 1. The traceability of direct current is based on a Josephson standard cooled in liquid helium.

Ilkka Iisakka, Researcher, Tel +358 50 410 5519,[email protected]


Calibration of direct voltage and current

Calibration servicesIn addition to accredited calibration laboratories, MIKES provides services to all customers requiring low measurement uncertainty. The most important calibration subjects in the field of direct current are solid state voltage standards, dc- and multifunction calibrators as well as precision multimeters. Zener standards are calibrated usually by comparison to MIKES working standards. A relay scanner connects the voltage difference of the standards to a nano-voltmeter and the results are recorded at regular in-tervals for a couple of weeks. Routine calibrations of direct voltage and current ranges of calibrators and multimeters are carried out using a reference multi-meter and a multifunction calibrator. The measuring ranges and uncertainties of calibrations for voltages up to 1 kV are presented in table 1.

Direct current calibrations are usually performed for currents between 0.1 mA and 1 A with relative un-certainty of 10 μA/A and for 100 fA – 100 μA with uncertainties varying from 600 μA/A to 20 μA/A.

When lower uncertainties are needed, calibrations can be performed by using directly the MIKES Jo-sephson standard. On special order, calibrations of multimeters and calibrators can also be carried out using directly the Josephson and Zener standards and a resistive voltage divider. Direct current calibra-tions requiring lower than 10 μA/A uncertainties and measurements above 1 A current levels can be per-formed by measuring the voltage across a resistan-ce standard. The lowest achievable uncertainties of these measurements can be found in table 2. Resis-tive voltage dividers are calibrated by comparison to the MIKES reference divider or with the Josephson standard. The value of voltage or current together with its uncertainty is given in the calibration certi-

Figure 2. A Zener direct voltage standard.

Device Zener-standard Calibrator or multimeterVoltage (V) 1 1.018 10 0 ... 10 10 ... 100 100 ... 1000Uncertainty (μV) 0.2 0.2 2 0.3 ... 20 70 ... 610 1000 ... 10000

Table 1. The smallest measurement uncertainties for the most common direct voltage calibrations. By using special te-chniques even much lower calibration uncertainties can be achieved.

ficate. Stability or temperature dependence measurements can be carried out on custo-mer’s request. MIKES follows the longterm stability of customers’ voltage standards and can attach follow-up results to the calibration certificate if needed.

In addition to the calibration, we carry out special assignments related to voltage and current measurements and actively partici-pate in research and development projects in these fields.

Current < 0.1 pA (0.1 ... 100) pA (1 ... 100) nA (0.1 ... 100) μA (0.1 ... 100) mA (0.1 ... 20) AUncertainty 0.1 fA (1 ... 0.6) mA/A (0.1...2) pA 20 μA/A 5 μA/A (5 ... 20) μA/A

Table 2. The smallest uncertainties of direct current calibrations for currents less than 20 A.


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Calibration of alternating voltage and current


In society, many important functions such as the measurement of electrical energy, which is supp-lied by electrical power networks to consumers, are based on the accurate measurement of alternating voltage and current. MIKES is responsible for the traceability of alternating voltage and current in Fin-land. The traceability of the most accurate measure-ments of AC voltage is based on thermal converters and range resistors acting as secondary standards. The traceability of AC voltage and AC current ranges of multifunctional calibrators and precision multime-ters comes from AC voltage standards calibrated at MIKES or at other national metrology institutes and from their calibrated range and shunt resistors. The reliability of results is verified by taking part in interna-tional comparisons.

MIKES performs also high level research on AC vol-tage metrology. Especially, MIKES is at the top of in-ternational metrology research in development work of two different types of AC voltage standards in do-mestic collaboration with VTT: a primary standard for AC voltage based on Josephson effect and an AC voltage working standard based on micromechanical sensors (MEMS).

Figure 1. Equipment of the national metrology laboratory for alternating voltage and current.

MIKES, Tekniikantie 1,02150 EspooTel +358 20 722 111 www.mikes.fi

Tapio Mansten, Senior Research Scientist, Tel +358 400 767 427,[email protected]


Figure 2. AC-DC-relay and two thermal convertes.

Calibration servicesMIKES has accurate AC voltage meters and calib-rators as working standards. We calibrate voltages from 1 mV to 1000 V in a frequency range from 10 Hz to 1 MHz and currents from 100 μA to 20 A in a frequency range from 50 Hz to 10 kHz (up to 8000 A in the frequency range 45 Hz …. 65 Hz). Typical devices that we calibrate include: thermal conver-ters, precision multimeters and calibrators and cur-rent sources and sensors. Also, other devices can be calibrated in agreement with a customer. Usu-ally customer’s AC voltage and current devices are calibrated by comparing their AC/DC difference to the AC/DC difference of a Fluke 5790A working stan-dard and Fluke A40 AC/DC current shunts or by com-paring the rms values directly to the rms value of a MIKES device. The measuring ranges and smallest achievable uncertainties for these calibrations are shown in the tables below.

Table 1. Measurement ranges and smallest relative uncertainties in parts per millions from measurement results (μV/V) for the alternating voltage range of a multifunctional calibrator.

Frequency10 Hz 20 Hz 40 Hz 53 Hz 400 Hz 1 kHz 10 kHz 20 kHz 50 kHz 100 kHz 500 kHz 1 MHz

1 mV 1200 1200 1200 - 1200 1200 1200 1200 1200 1400 3300 50002 mV 590 590 590 - 590 590 590 590 590 680 1600 460020 mV 130 120 120 - 120 120 120 120 120 140 350 580100 mV 50 50 30 - 30 30 30 30 35 60 220 4501 V 40 40 20 - 15 15 15 15 30 50 110 44010 V 40 40 20 - 20 20 20 20 30 45 140 400100 V 40 40 30 - 20 20 20 20 35 40 - -1000 V - - 50 50 50 - - - - - - -

Table 2. Measurement ranges and smallest relative uncertainties in arts per million of measurement result (μA/A) for the alternating current range of a multifunctional calibrator.na mittaustuloksesta (µA/A).

Frequency40 Hz 400 Hz 1 kHz 5 kHz 10 kHz

100 µA 80 80 80 90 110

1 mA 35 35 35 35 40

10 mA 35 35 35 35 50

100 mA 35 35 35 35 601 A 35 35 35 50 11010 A 110 110 110 150 21020 A 110 110 110 180 260

Calibration of altrnating voltage

Cur

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(rm

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Volta

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Calibration of capacitance and inductance standardsTapio Mansten, Senior Research Scientist, Tel +358 400 767 427,[email protected]


Capacitors and inductors are essential components in electronics. Moreover, capacitive sensors are used in many high-precision measurements: e.g. in measure-ments of position, distance and level. For calibration of precision LCR meters, inductance and capacitance standards are needed. Therefore, traceable measu-rements of capacitance and inductance are of utmost importance. In Finland, MIKES is responsible for the traceability of capacitance and inductance.

In MIKES, ac coaxial bridges are used to provide traceability of the decade capacitance standards in the range 10 pF – 1 μF to resistance and frequen-

Figure 1. Traceability to capacitance from resistance and frequency in MIKES impedance laboratory.

cy — quantities which are maintained at MIKES. The reliability of the results is verified by international comparisons and by taking advantage of capacitance measurement services at the BIPM. The capacitance values between calibration points are interpolated by using measuring bridges based on inductive dividers.

Inductance standards in the range 100 μH – 100 mH are traceable to the MIKES capacitance and resistan-ce standards.

Calibration servicesMIKES calibrates capacitance standards in the range 0 pF up to 1 μF by using a very stable capacitan-ce bridge and reference capacitance standards. The measurements are usually carried out at 1 kHz but other measurement frequencies are also possible. The calibration is performed using either two-terminal or three-terminal method by connecting the calibrat-ed capacitance standard through a 16-channel coa-xial relay to the capacitance bridge and by measuring automatically for about two or three days. The device under calibration is placed together with a Pt-100 sensor into a volume having a constant temperature. The temperature is varied during the measurement by about one or two degrees in order to measure the temperature coefficient of the device under calibra-tion. The results are corrected to the temperature of 23 °C.

Traceability of inductance standards at MIKES is ba-sed on the link to the capacitance (100 pF) standards which are calibrated at BIPM and the resistance stan-dards, calibrated from the Quantum Hall Resistance in MIKES. The 100 mH inductance is linked to capa-citance standards at 1 kHz and 1.59 kHz with the use of series resonance method, where 253 nF and 100 nF capacitors are used as references.



Calibration of capacitance and inductance standards

Capacitance value 10 pF 100 pF 1 nF 10 nF 100 nFRelative uncertain-ty (µF/F)

5 5 10 30 100

Figure 2. AH2500A measuring bridge and a 1-nF capacitan-ce standard under calibration.

Table 1. Measuring ranges and smallest calibration uncertainties at MIKES for calibration of capacitive standards at 1 kHz frequency. The expanded relative uncertainty (k = 2) is expressed as parts per million of measured capacitance.

Capacitance value 0 pF - 10 pF 10 pF - 1 nF 1 nF - 10 nF 10 nF - 100 nF 100 nF - 1 μFRelative uncertain-ty (µF/F)

10 (+ 5 aF) 10 30 200 400

Table 2. Measuring ranges and smallest calibration uncertainties at MIKES for calibration of capacitive standards that have capacitance values smaller than 10 pF or larger than 100 nF or whose value is not even decade. The expanded relative uncertainty (k = 2) is expressed as parts per million of measured capacitance. For capacitances lower than 10 pF a base apacitance of 5 aF is added to the uncertainty.

Table 3. Measurement methods, inductance values, and reference standards used in calibration of induc-tance standards at 1 kHz.

Method Inductance Impedance 1 kHz Reference Uncertainty 2sRelative uncertain-ty (µF/F)

5 5 10 30

2 DVM 0.1 mH 1 W 1 W 502 DVM 1 mH 10 W 10 W 502 DVM / SR 10 mH 100 W 100 W 20SR / 2 DVM 100 mH 1 kW 253 nF / 100 W 20

Sampling method, which is based on the use of 2 DVM is used to define the values of inductance stan-dards in the range 100 μH – 10 mH. Impedance of the calibrated inductors is compared with the impe-dance of the reference resistor, by measurements of the voltage ratios at frequencies below 1 kHz.

In addition to the calibration of capacitance and in-ductance standards, we carry out special assignme-nts related to impedance measurements and actively participate


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Calibration of resistance

Ilkka Iisakka, Researcher, Tel +358 50 410 5519, [email protected]


Resistance is the most important quantity of electrical measurements together with direct voltage. In addi-tion to resistance calibrations, resistance standards are needed for providing traceability to other elect-rical quantities. MIKES is the national standards la-boratory of resistance. The traceability of resistance standards at MIKES is based on its own quantum Hall standard, which connects the unit of resistance to the values of physical constants with a relative uncertain-ty of 10–8. The dissemination to secondary and wor-king standards, which are stored in oil or air baths, is performed by using a cryogenic current comparator or a direct current comparator resistance bridge. The

traceability of resistance standards with value above 1 GΩ is realized by using a modified Wheatstone brid-ge.

The accuracy of MIKES’s resistance standard ca-librations is at high international level, confirmed by good results in international resistance comparisons. MIKES has also participated in coordination of inter-national key comparisons, in which the accurate re-sistance transfer standards developed at MIKES have been used.



Calibration of resistance

Calibration servicesIn addition to accredited calibration laboratories, MI-KES provides services to all customers requiring very low measurement uncertainty. In resistance calibra-tion the resistance of the device under calibration is measured and the uncertainty of the measurement re-sult is calculated. On demand, temperature, power, orvoltage dependence of resistance standards can be determined, too. MIKES follows the long-term stability of customer’s resistance standards and when request-ed attaches the results to the calibration certificates. In addition to resistance standards, other calibration services for calibration of precision multimeters and multifunction calibrators are offered.

In the range 0.0001 Ω ... 100 MΩ, the resistance stan-dards are calibrated by comparing them to the prima-

ry and working standards of MIKES by using a MI 6242B resistance bridge. When special accuracy is needed, the measurements can be carried out by using a cryogenic current comparator. In the range 1 MΩ ... 100 TΩ, a modified Wheatstone bridge is used. During the calibration, the resis-tance standards are placed in a thermal bath. Either two point or four point measurements are used and when needed a guarded measurement is carried out. The resistance ranges of multime-ters are calibrated by using MIKES multimeters.

In addition to calibrations, we provide special as-signments related to resistance measurements and actively participate in research and develop-ment projects in this field.

Figure 1. Measurement ranges and measurement uncertainties for resistance standards.


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The measurement of electric energy consumption has a huge economic importance. Through the de-velopment of electric energy market, the importance of measurement accuracy and traceability is further emphasised. Accurate electric power standards are required in the calibration of energy meters. At MI-KES, measurements of electric power at 50 Hz are traceable to SI units through a sampling power stan-dard. Calibrations are performed using either sing-le-phase or three-phase measurements. Typical de-vices that we calibrate are electric power meters and converters.

At MIKES power laboratory, the traceability of elect-ric power at 50 Hz is based on direct voltage from a Josephson standard and resistance realised by a quantum Hall equipment. The sampling power stan-dard consists of two 8½ digit voltmeters, which are accurately synchronised. Currents smaller than 20 A are converted to voltages using specially construct-ed shunt resistors, whose resistance values are traceable to the quantum Hall resistance standard. As a result of the construction of the shunts, their frequency dependence is very small. Measurement results of voltage meters are based on fast sampling and traceable to the Josephson voltage standard. The same measurement equipment together with a current sensor based on a Rogowski coil is used to measure currents and current ratios up to 8000 A. The measurement uncertainty of the MIKES power reference equipment is 0.005 % at its best.

Figure 1. In power and energy measurements tracea-bility for large currents is also needed. Parts of 8000 A measuring setup based on a Rogowski coil.

The methods and equipment of MIKES power labora-tory represent international top quality. The high quali-ty of measurements is verified by taking part in in-ternational comparison measurements together with national metrology laboratories from other countries. MIKES is also an active member in different expert working groups at international level and takes part in national as well as international joint research proje-cts. Several projects are in the European Metrology Research Programmes EMRP and EMPIR..

Calibration of power andenergy at line frequency

Pekka Immonen, Researcher, Tel +358 50 410 5520, [email protected]

Esa-Pekka Suomalainen,Senior Research Scientist, Tel +358 50 382 2463, [email protected]



Calibration of power and energy at line frequency

Calibration servicesMIKES calibrates especially reference standards of customers who need the best available measuring accuracy. Typical instruments are power compara-tors and converters. The calibrations are performed by connecting the same current and voltage to the customer’s device and the reference meter of MI-KES. If necessary, effect of the power source used in the calibrations is minimized by accurately synchro-nising the meters. The reference meter used in the calibrations is either a single-phase sampling power standard or a three-phase power comparator.

Measured quantity Expanded relative uncertainty (k = 2)Single phase, 30 V – 500 V, 5 mA – 10 AActive power 50 μW/VAReactive power 100 μvar/VA3-vaihe, 50 V – 350 V, 5 mA – 12 AActive power 120 μW/VAReactive power 250 μvar/VAActive energy 120 μWh/VAhReactive energy 250 μvarh/VAh

Table 1. Measuring ranges and calibration uncertainties at MIKES for calibrations of power and energy at line frequency.

In addition to power standards, we calibrate current and voltage transformers and transducers up to 200 kV voltage and 8 kA current. We carry out special assignments related to the measurement of elect-ric power and energy and take part in research and development cooperation projects in this field. Mo-reover, we organise educational opportunities in this field and custom tailored training.

Figure 2. A coaxial shunt resistor of the sampling power standard.


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RF- and microwavecalibrationsKari Ojasalo, Researcher, Tel +358 50 410 [email protected]


The importance of measurement reliability is empha-sized along with the continuously increasing amount of applications in RF- and microwave ranges. MIKES is the national metrology institute in this field and of-fers traceability with low uncertainty to internationally accepted measurement standards in RF and micro-wave power measurements and measurements of S parameter (reflection and attenuation). We calibrate power sensors and attenuators for instance.

Our calibration equipment is equipped with precision type N connectors, thus our measu-rement range ex-tends to 18 GHz. The measurements and the analysis

Figure 1. Measurement of power sensors.

of results are mainly automated. The measurements are carried out in a controlled 23 °C temperature in an electromagnetically shielded room.

The high standard of the measurements is verified by actively taking part in international comparisons together with other national metrology institutes. The traceability is based on power and attenuation calib-rations at NPL (National Physical Laboratory) in U.K. and on the primary standards at MIKES.


RF- and microwave calibrations

Calibration services

Power

The calibration coefficients of sensors are deter-mined with measurement equipment based on a power divider. Measurement of reflection coefficient by using a vector network analyzer is included in the sensor calibration. Typically, calibration takes five workdays. The calibration of the absolute power of a power reference in a power meter is performed for thermocouple and diode power sensors. The reflec-tion coefficient of the power source is determined at the same time.

Attenuation

Attenuation calibrations are carried out by traceable vector network analyzer measurements. Determi-nation of reflection coefficient by is included in the calibration. We calibrate fixed value attenuators as well as step attenuators. The step attenuators can be controlled by using a GPIB bus, RS-232 connection or directly using the step attenuator controller Agilent 11713A..

Reflection coefficient

Traceable measurements of reflection coefficient are performed using a vector network analyzer. The impedance of the impedance standards used in the measurements is determined at MIKES with accurate dimensional measurements. Dimensional measure-ment services for N-type airlines are offered for cus-tomers, also.

Figure 2. Measurement of reference step attenuator.

Table 1. Measurement ranges and uncertainties

Figure 1. Measurement set-up for power sensors.

Quantity Measurementrange

Measurementfrequency range

Uncertainty

Calibration coefficientsof power sensors

1 mW 10 MHz – 18 GHz(1) 0.4 % – 1.1 % (k=2)(2)

Absolute power 1 mW 10 MHz – 18 GHz(1) 4 mW/W – 11 mW/W (k=2)

Attenuation 0 dB – 80 dB 300 kHz – 6 GHz 0.02 dB – 0.17 dB (k=2)

Attenuation 0 dB – 60 dB 6 GHz – 18 GHz 0.05 dB – 0.18 dB (k=2)

Reflection coefficient (realand imaginary parts)

-1 ja 1 välillä 10 MHz – 18 GHz 0.013 – 0.024 (k=2,45)(3)

1) Tehon kalibrointitaajuudet ovat: 10, 30, 50, 100, 300, 500 MHz, 1 GHz, 1.5 GHz, 2 GHz – 18 GHz 1 GHz askelin.2) Heijastuskertoimen itseisarvo ≤ 0.083) Kompleksimuuttujan kompleksiselle epävarmuudelle 95 % kattavuus saadaan, kun k=2.45.


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High voltageand high currentEsa-Pekka Suomalainen, Senior Research Scientist, Tel +358 50 382 2463 [email protected]

MIKES, Tekniikantie 1,02150 EspooPuh. 020 722 111 www.mikes.fi

High voltage quantitiesThe importance of high voltage measurements has been emphasized with the opening of electricity mar-kets. The quality of electricity, transmission losses and the sale of electricity for industry and for private households have become more important measu-ring and monitoring subjects. In addition to electricity, electronics and information industries, high voltage users can be found, in almost every industrial sec-tor. High voltage metrology at MIKES is internatio-nally respected and provides services on traceability also at customers premises in Finland and globally.

TraceabilityThe high voltage measurements at MIKES are traceab-le to capacitance, resistance and voltage, which in turn are based on quantum primary standards: quan-tum Hall resistance standard and Josephson voltage standard. We have performed well and also acted as a coordinator in international comparisons in high voltage metrology. As an example of this is the coor-dination of broad European and worldwide compari-sons of lightning impulse voltage measuring systems.

Jussi Havunen, Research Scientist, Tel +358 50 590 [email protected]


High voltage and high current

Quantity Measurement range Uncertainty (k=2)Direct voltage 1 kV - 1000 kV 0.0005 - 0.01 %Alternating voltage, voltage ratio 1 kV - 200 kV 0.002 - 0.01 %– angle error 0 - 100 mrad 0.02 mradAlternating current, current ratio 1 A - 6 kA 0.025 - 0.02 %– angle error 0 - 100 mrad 0.2 - 0.4 mradCapacitance 1 - 100 kV / 10 pF - 200 µF 0.002 - 0.05 %

-– loss coefficient tan δ 1.10-5 - 2 1 % (1.10-5 abs)Inductance / losses 1 µH - 10 H 0.03 % / 0.2 mradLightning impulse 50 mV - 400 kV 0.1 - 0.5 %Switching impulse 1 V - 200 kV 0.1 - 0.2 %Other voltage impulses (e.g. surge) 1 V - 400 kV 0.1 - 0.5 %Current impulses 1 A - 10 kA 3 %ESD-pulssi 1 A - 50 A 5 %Time parameters of pulses 0.7 ns - 100 ms 0.5 - 5 %Apparent charge of a pulse (partial discharge) 1 pC - 1 nC 2 % (0.2 pC abs)

Calibration servicesMIKES offers calibration services for almost all high voltage quantities and measuring systems up to 200 kV voltage. The range of alternating current calibra-tions extends to 6 kA. The measuring range for pulse quantities covers a voltage range from millivolts up to megavolts and currents up to tens of kiloamperes. Our expert services cover different aspects of calib-ration of measuring systems. If wanted, we evaluate customer’s measuring systems and modify them to be more accurate and stable if needed. In future, our area of qualification will be extended to calibrations related to measurements on the quality of electricity.

The best calibration uncertain y is achieved when calibrations are performed in a laboratory at MIKES but calibrations can be carried out at customer’s pre-mises, also. Measuring systems can be calibrated on-site when the voltage level, the size of the system, grounding conditions or proximity effects necessitate it.

Calibration subjectsDevices that we calibrate include:

• voltage dividers • voltage and current transformers • measuring probes, voltage and current sensors and current shunts • high voltage inductors and capacitors • transient recorders, peak voltage meters • surge-, EFT- ja ESD- test devices • voltage testers • pulse calibrators • partial discharge calibrators

Table 1. Calibration services of high voltage


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Acoustic calibrations

MIKES, Tekniikantie 1, 02150 EspooTel +358 20 722 111 www.mikes.fi

Jussi Hämäläinen, Researcher, Tel +358 50 410 [email protected]

The need of accurate acoustic measurements is gro-wing for instance due to regulations and legislations concerning noise emissions and exposure to vibra-tions. A good measurement accuracy requires, in ad-dition to high-quality measurement devices, regular and traceable calibrations. In Finland, MIKES is res-ponsible for the traceability of the acoustic quantities: sound pressure and acceleration.

Sound pressure is transformed into an electrical sig-nal by using accurate condenser microphones, who-se primary calibration equipment is in use at MIKES. Sound level calibrators are calibrated using these condenser microphones. The traceability chain of sound pressure level starts from the calibration of laboratory grade microphones by using a so-called reciprocity calibration system. This calibration gives

Figure 1. A reciprocity ca-libration of microphones is starting in the soundproof laboratory at MIKES.

the voltage-pressure sensitivities of the microphones. The method is described in the standard IEC 61094-2 (1992-03) and it is in use in severalother national metrology institutes.

A vibration transducer produces a signal, typically a voltage or a charge, which is proportional to the ac-celeration of mechanical motion. Therefore, in the calibration of a vibration transducer, the sensitivity (typically mV/(m/s2) or pC/(m/s2) of the sensor is de-termined as a function of frequency. MIKES calibrates vibration transducers by comparing their readings to a known vibration produced with a vibration exciter. The real amplitude of acceleration and frequency is si-multaneously measured by using a reference sensor. The method is described in the standard ISO 16063-21:2003.

Kari Ojasalo, Researcher, Tel +358 50 410 [email protected]


Acoustic calibrations

Figure 2: The measurement ranges and uncer-tainties of calibration of vibration transducers.

Type ofmicrophone

Taajuus [kHz] Uncertainty [dB]

LS 1

0.0315 0.060.063 ... 2 0.044 0.055 0.068 0.0810 0.10

LS 2

0.0315 0.080.063 0.060.125 ... 8 0.0510 0.0612.5 0.0816 0.1020 0.14

Calibration services

Microphones

We calibrate ½ (LS2P) and 1 (LS1P) inch condenser microphones described in the standard IEC 61094-1 (Table 1). The calibration method depends on the ac-curacy required by the customer. The smallest calib-ration uncertainties can be achieved by using the re-ciprocity method. In many cases, a comparison with a reference microphone by a sound level calibrator is adequate.

Type of calibrator Frequency (Hz) Sound level [dB re 20 μPa] Uncertainty [dB]Single-frequency 125 – 1000 70 – 130 0.08

Multi-frequency31,5 94 – 114 0.15

63 – 4000 94 – 114 0.108000 - 12500 94 - 114 0.15

Table 1. Uncertainties of calibration for measurementmicrophones.

Table 2. Calibration ranges and uncertainties for sound level calibrators. The type of the measurement

Sound level calibrators

The most common devices calibrated at MIKES acoustics laboratory are sound level calibrators and pistonphones. We calibrate the sound pressure levels at fixed frequency points. At the same time, the distortion and frequency of the sound source is measured (Table 2).

Vibration transducers and loggers

We calibrate vibration transducers, loggers and vibration measurement devices in the frequency range 1 Hz – 10 kHz. Typical nominal acceleration is 10 m/s2. The calibration gives the magnitude and the phase of the sensitivity of the vibration trans-ducer. The uncertainty of the calibration depends on the transducer under calibration. Typical uncer-tainties for the magnitude are 1–3 % and for the phase 1–2° depending on the frequency (Figure 2).


Mass, pressure flow



Calibration of time,time interval,and frequency

MIKES, Tekniikantie 1,02150 EspooTel 358+ 20 722 111 www.mikes.fi

Figure 1. The traceability of time and frequency is based on hydrogen ma-sers (in the figure above) and on cae-sium atomic clocks, which are located in enclosures having with a special climate control.

Measurements of frequency and time interval are needed in various direct and indirect measurements, e.g., in telecommunication; therefore, precise and traceable frequency and time interval measurements are important nationally. The importance of absolute time is increasing, too (e.g. time stamps).

MIKES is responsible for the traceability of time, time interval, and frequency in Finland. MIKES time laboratory maintains the official time in Fin-land with an uncertainty of 10 ns in relation to the coordinated universal time (UTC) and national frequency with a 1•10-13 relative uncertainty. The reference standards for time and frequency are one caesium atomic clock, four hydrogen masers and several GPS receivers. Finland participates in maintaining of the UTC with its five reference standards through GPS based time comparison.

Mikko Merimaa, Principal Metrologist, Tel 358+ 50 410 5517 [email protected]

Ilkka Iisakka, Researcher, Tel 358+50 410 5519, [email protected]


Calibration of time, time interval, and frequency

Figure 3. Stabilities of various frequency standards as a fun-ction of integration time.

Calibration servicesWe calibrate e.g. GPS receivers (frequency), os-cillators, time interval counters, stopwatches, stro-boscopes, and optical tachometers. The frequency range is 1 mHz to 5 GHz. We make time interval measurements according to customer’s need, with a lower limit of approximately one nanosecond. Furt-hermore, MIKES has a transmitter for time code and precise 25 MHz frequency for those near the Helsin-ki metropolitan area who need precise time and fre-quency.

In addition to calibration, we carry out special assig-nments related to time and frequency measurements and participate in research and development collabo-ration projects in this field.

NTP - network time serviceComputer clocks can be synchronised with the natio-nal time in Finland maintained by MIKES by using Network Time Protocol, NTP. The achievable uncer-tainty depends on network connections but it is around one millisecond at its best. MIKES maintains NTP ser-vers subject to charge for institutions and companies. We have four servers of the highest level (stratum-1): two of them are synchronised directly to MIKES ato-mic clocks and two to GPS receivers. Moreover, we control two public NTP servers that are locked to MIKES servers. These servers are available free of charge for public use.


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Electricity time acoustics Optics Length

geometry Chemistry

Optical quantities

MIKES Aalto Mittaustekniikka, Otakaari 5A, 02150 Espoohttp://metrology.tkk.fi

Farshid Manoocheri, TkT, Tel +358 9 470 22337,[email protected]

Petri Kärhä, TkT, Tel +358 9 470 22289,[email protected]

MIKES-Aalto MetrologyResearch InstituteMetrology Research Institute (MIKES-Aalto Mittaus-tekniikka) is a joint laboratory of Aalto University and MIKES. It is the national standards laboratory of opti-cal quantities in Finland. The laboratory is a research and education unit belonging to the Department of Signal Processing and Acoustics at the Aalto Univer-sity. The laboratory carries out basic research on LED measurements, temperature measurements, optical properties of materials, measurement electronics and on various measurement methods of photometry and radiometry. In addition to calibration services, the la-boratory offers expert services and educates Diploma Engineers (M. Sc.) and Doctors of Technology for de-manding professional tasks in academy and industry.

Figure 1. Integrating sphe-re is used as a light source in calibration of luminance and radiance. The sphere has a uniform spatial distri-bution of the outcoming light intensity.

Research activitiesResearch activities and assignments of a national standards laboratory require continuous internatio-nal cooperation. International comparisons have an essential role in creating traceability chains and veri-fying measurement uncertainties. The laboratory has an active role in, e.g. EURAMET, CCPR, and CIE or-ganisations and takes actively part in the EU research programs.


Optical quantities

Figure 3. Part of the calibrations can be car-ried out as field calibrations at customer’s laboratory premises. A filter radiometer de-veloped in our laboratory for calibration of spectral irradiance or illuminance of stan-dard lamps is shown in the figure.

Calibration servicesMetrology Research Institute offers calibration services to the optical quantities listed in the following table. All measurements are traceable to national and international measurement stan-dards. Measurement uncertainties are verified by international comparison measurements. We are pleased to give further information, e.g. on the contents of calibration services and on the measurement uncertainty in different measure-ment and wavelength ranges.

Calibration objectslInstruments that we calibrate include among others:

• illuminance meters• standard lamps• radiance and luminace meters• laser power meters• optical filters• reflectance references• UV-meters• fluorescent samples

Figure 2. The spectral irradiance of a lamp is measured by positioning the lamp at an accurately determined distance from a radiometer, whose spectral responsivity and surface area are known.

Quantity Measurement range Wavelength range Uncertainty (k=2)Luminous intensity 1 – 10 000 cd - 0.5 %IlluminanceIlluminance responsivity 0.1 – 5 000 lx - 0.5 % - 0.7 %

LuminanceLuminance responsivity 1 – 40 000 cd/m2 - 0.8 % - 1.0 %

Luminous flux 10 – 10 000 lm - 1.0 %

Spectral irradiance 100 μW m-2 nm-1 – 500 W m-2 nm-1 290 – 900 nm 0.8 % - 2.9 %

Spectral radiance 100 μW m-2 sr -1 nm-1 – 1 W m-2 sr -1 nm-1 360 – 830 nm 1.4 % - 4.2 %

Color coordinates (x, y) 0.1 – 0.9 - 0.0005Color temperature 2800 – 3250 K - 5 KOptical power 0.1 – 0.5 mW 325 – 920 nm 0.05 % - 1.0 %

Spectral responsitivity 0.01 – 20 μW 0.05 – 5.0 mW

380 – 1700 nm 250 – 380 nm

0.5 % - 4.0 % 2.0 % - 5.0 %

Transmittance 0.0001 – 1 250 – 1700 nm 0.2 % - 5.0 %Absorbance 0 – 4 250 – 1700 nm 0.0009 – 0.022Regular reflectance (5° – 85°) 0.01 – 1 250 – 1000 nm 1.0 % - 5.0 %Diffuse reflectance factor 0.1 – 1 360 – 830 nm 0.4 % - 1.0 %Fiber optic power(in collaboration with MIKES)

1 nW – 200 mW 1310 – 1550 nm 1.2 % - 2.0 %


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geometry Chemistry

Quantitave Microscopy - Atomic Force MicroscopeVirpi Korpelainen, Senior Research Scientist, Tel. +358 050 410 5504 [email protected]

Development and research in nanotechnology has in-creased the need for accurate measurements in re-search institutes and industry. Different kinds of Scan-ning Probe Microscope (SPM) measurements are commonly used in many institutes and companies. In order to guarantee accurate and reliable dimensio-nal measurements at nanometre range, MIKES has a traceably calibrated Atomic Force Microscope (AFM). Thus, MIKES can provide customers with traceable measurements also at nanometre range.

MIKES provides accurate AFM measurement ser-vices to match the needs of customers. In addition we calibrate SPM transfer standards.

Figure 1. Alignment of laser beams for interferometric calib-ration of y axis of the AFM.



Quantitave Microscopy - Atomic Force Microscope

Property DataSample size <100 mm × 100 mmSample thickness <20 mmSample mass <500 gMeasurement range (xy) 100 µm × 100 µmMeasurement range (z) 12 µmResolution (xy) 0.15 nm

0.02 nm (low voltage mode*)Resolution (z) 0.05 nm

0.01 nm (low voltage mode*)

Uncertainty (k=2), x and y directions

Q [3; 2 L/µm] nm

Uncertainty (k=2), z direction

Q [3; 2 L/µm] nm

Q [x; y] = (x2 + y2)1/2

MIKES has a PSIA XE-100 AFM, which is calibrat-ed interferometrically and with grating calibrated by laser diffraction at MIKES. The AFM is traceable to the definition of the metre. The xy-movements of the AFM are mechanically separated from the z-move-ments. This increases the linearity of the movements, decreases out of plane movements and eliminates cross-talk. The structure of the device allows rather large samples to be measured, also measurements can be done using the most usual measurement mo-des: contact, non-contact, tapping and lateral force. The measurement results can be analysed using SPIP software 1.

Scale errors of uncalibrated SPMs typically range from 2 % to 20 %. In addition measurement errors may cause distortions in the measured figure, which might be difficult to detect from the figure. Therefore, the device has to be calibrated. New, more advan-ced SPMs have increased measurement precision, but the development does not remove need for ca-libration. Especially in all quantitative form measure-ments, the measurements should be traceable to the definition of the metre. Usually SPMs are calibrated by using calibrated transfer standards.

1 The Scanning Probe Image Processor SPIPTM http://www.imagemet.com

Figure 2. 2-D grid standard.

Figure 3. AFM image of Seeman tile type DNA nano-origami structures.


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geometry Chemistry

Characterization of nanoparticles

Nanoparticles are widely used in many applications. Accurate characterization of the nanoparticles is im-portant in research, production and applications in se-veral fields including industry, health, safety and relat-ed regulation. At VTT MIKES metrology the particles can be characterized using two different methods: Dynamic Light Scattering (DLS) and atomic force mi-croscopy (AFM). The measurements are traceable to the definition of the metre via MIKES interferometri-cally traceable metrological atomic force microscope (IT-MAFM). Both methods have advantages and limi-tations. DLS is fast method and the results are statis-tically representative. In DSL measurements even a small number of large particles can prevent detection of small particles. AFM can be used to measure both size and shape of single particles. The disadvantage of AFM measurements is that only limited number of particles can be measured which leads to poor sta-tistics. Tip sample interaction is important especially when measuring small particles. Also sample prepa-ration might be challenging.

Figure 1. AFM image of 100 nm nanoparticles

Figure 2. DLS measurements

Instrument Zetasizer Nano PSiA XE-100Measurement method DLS AFM

Measurands Size distribution,Zeta potential

Size,Shape

Measurement range 0,3 nm - 10 µm 5 nm – 5 µm

Measurement uncer-tainty

2 % from 1 nm

Table 1. VTT MIKES metrology has two instruments suitable for nano-particle measurements.

Virpi Korpelainen, Senior Research Scientist, Tel. +358 050 410 5504 [email protected]



The services for nanoparticle cha-racterization at MIKES

• Nanoparticle size and shape measurements using AFM • Nanoparticle size distribution in solution using DLS • Nanoparticle surface charge (Zeta-potential) measurements in solution

Zetasizer Nano

Dynamic Light Scattering is used to measure particle and molecule sizes. This technique measures the dif-fusion of particles moving under Brownian motion, and converts this to size and a size distribution using the Stokes-Einstein relationship.

Laser Doppler Micro-electrophoresis is used to measure zeta potential. An electric field is applied to a solution of molecules or a dispersion of particles, which then move with a velocity related to their zeta potential.

Characterization of nanoparticles

Atomic force microscopy (AFM)An AFM uses a cantilever with a very sharp tip to scan over a sample surface. As the tip approaches the surface, the close-range, attractive force between the surface and the tip cause the cantilever to defle-ct towards the surface. However, as the cantilever is brought even closer to the surface, such that the tip makes contact with it, increasingly repulsive force ta-kes over and causes the cantilever to deflect away from the surface.

In AFM images the topography of a sample surface by scanning the cantilever over a region of interest. The raised and lowered features on the sample surface influence the deflection of the cantilever, which is mo-nitored by a position-sensitive photo diode (PSPD). By using a feedback loop to control the height of the tip above the surface the AFM can generate an accu-rate topographic map of the surface features.

Figure 3. DLS results of ~100 nm nanoparticles


Mass pressure flow



geometry Chemistry

Calibration of laserinterferometersJeremias Seppä, Senior Research Scientist, Tel +358 50 410 [email protected]

Veli-Pekka Esala, Senior Research Scientist, Tel +358 40 866 [email protected]


Laser interferometers together with gauge blocks are the most important measurement standards in mo-dern length metrology. At 1980s a common unders-tanding was that laser interferometers are accurate and hence do not need any calibration. However, ever increasing demand for accuracy and long expe-rience on usage of laser interferometers have shown that it is necessary to calibrate laser interferometers, also. At MIKES, we have traceable procedures to ca-librate laser interferometers. The calibration of laser interferometers improves their reliability and accu-racy essentially.

Figure 2. An iodine-stabile HeNe-la-ser used for the practical realisation of the metre.

Figure 1. Functional testing of a laser interferometer


Calibration of laser interferometers

Figure 3. Errors in environmental sensors can have remar-kable effects on the readings of a laser interferometer..

Calibration procedure

Calibration of laser frequency

The vacuum wavelength of lasers used in laser inter-ferometers is calibrated using iodine-stabilised lasers. Traceability to the definition of the metre is guaran-teed as frequencies (vacuum wavelength) of the iodi-ne-stabilised lasers are determined by an optical fre-quency comb refer-enced to an atomic clock.

MIKES maintains the following lasers that are locked to iodine absorption lines according to international recommendations: He-Ne lasers at wavelengths: 633 nm (Figure 2) and 543.5 nm and a Nd:YAG-laser at 532 nm. These laser have a relative frequency uncer-tainty better than 10-10 (expanded uncertainty, k=2).

The frequency of the laser under calibration is compa-red to the frequency of an iodinestabilized laser. The calibration includes a long term frequency (vacuum wavelength) calibration and repeatability measure-ments. Moreover, the frequency difference of the horizontally and vertically polarised lights is deter-mined and the separation of the polarisation planes inspected. Together these measurements provide good indication of the frequency stability of the laser under calibration. Lasers that operate at wavelengths not reachable by iodine-stabilized lasers can be calib-rated using a frequency comb.

Calibration and functional testingof environmental sensors

In addition to laser vacuum wavelength calibration the environmental sensors are calibrated and their ope-ration tested. These measurements are necessary to achieve the naturally good measurement accuracy of a laser interferometer. Especially, by calibrating the environmental sensors order of magnitude bettermeasurement accuracy can be achieved for alaser interferometer.

The calibration of environmental sensors includes the calibration of air temperature sensors, atmosphe-ric pressure sensors and material temperature sen-sors. The functional testing is performed in a tempe-rature stabilised laboratory room by measuring the locations of a moving carriage equipped with a retro-reflector with the laser interferometer under calibra-tion and with a reference laser interferometer (Figure 1). In these measurements, both laser beams tra-vel through the same optical components and data is collected with and without the environmental sen-sors operating. Also, the angle-scale is tested using a reference laser. If necessary, the quality of the optical components is tested with a flatness interferometer.

If the readings of the environmental sensors deviate remarkably from readings of the reference instru-ments they should be adjusted. By adjusting them, the accuracy of the laser interferometer can easily be improved (Figure 3), e.g. the adjustment is relatively easy to perform in Agilent laser interferometers.

TraceabilityThe frequencies of the iodine-stabilised lasers which are national measurement standards of length are determined using an optical frequency comb referen-ced to MIKES atomic clocks. The instruments used in the calibration of environmental sensors are calib-rated in the corresponding national standards labora-tories. Thus, the measurements are traceable to the corresponding definitions of the units.Quantity Measuring

rangeUncertain-

ty(k=2)Wavelength 633 nm; 543,5 nm;

532 nm~10-9 (suhteellinen)

Air pressure 970…1050 hPa (730…790 mmHg)

40 Pa

Air temperature 17…25 °C 0.10 °C

Materialtemperature

15…25 °C 0.050 °C Table 1. Uncertainty of calibration..


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geometry Chemistry

Interferometrical calibration of gauge blocksPasi Laukkanen, Research Engi-neer, Tel +358 50 382 9674, [email protected]

Antti Lassila, Pricipal Metrologist, Tel +358 40 767 8584 [email protected]


Figure 1. Tesa-NPL gauge block interferometer.

Calibration of gaugeblocksGauge blocks are the most important measure-ment standards of length in industry. Interferometric measurement of gauge blocks provides an absolu-te calibration method. By using interferometers, the practical realisation of the metre is transferred to a gauge block via the calibrated wavelength of the frequency-stabilised laser used in the interferome-ter. Gauge blocks calibrated by comparison must be traceable to gauge blocks calibrated by interferomet-ry. The length of a gauge block is defined in an ISO standard as the distance from the centre of the gauge face to an auxiliary reference plane wrung to the other end of the gauge block at 20 °C temperature and at 1013.25 hPa barometric pressure. Gauge block sets calibrated by interferometry give a lower uncertainty for mechanical calibrations for instance in accredited calibration laboratories.

Interferometers at MIKESMIKES have gauge block interferometers for short (0…300 mm) and for long (100…1000 mm) gauge blocks and end standards. The interferometers are located in a laboratory room having well stabilised environmental conditions and they are equipped with temperature, humidity and pressure sensors. Low un-certainties for refractive index of air and for thermal expansion compensation can be achieved with a pre-cise control and monitoring of the environmental con-ditions. Difference in surface roughness between the gauge block face and the reference plane is measu-red and corrected for in results. The parallelism and flatness of the surfaces can be measured, also.

The MIKES PSIGB interferometer for short gauge blocks (Fig. 1) uses stabilised He-Ne lasers at 633 nm and 543.5 nm. The interferometer is equipped

with a large wringing bed which enables fast and au-tomated calibration of even 14 gauge blocks in se-quence. In the Tesa interferometer, the gauge blocks are positioned vertically.

The long gauge blockinterferometer (Fig. 2) utilises white light and 633-nm laser light interference pat-terns. By using white light, beforehand knowledge of the length of the end standard is not required. The end standards and gauge blocks are positioned horizon-tally and supported at the Bessel points in such a way that the weight of the reference plane is compensated for.


Interferometrical calibration of gauge blocks

Device Measurement range Uncertainty (k=2)Gauge blocks, small 0.5 mm ... 300 mm Q[20; 0,3L] nmGauge blocks, long 100 mm ... 1000 mm Q[30; 0,11L] nmQuartz meters 1000 mm 72 nmL is measured in millimetres Q[x; y] = (x2 + y2)1/2

Figure 2. MIKES length bar interferometer for calibration of long gauge blocks.

TraceabilityThe regular calibration of length standards and length measuring equipment is a necessary part of measurement quality control. Traceable calibreations and knowledge on the measurement uncertainty are basic demands for good and constant quality. The traceability to gauge block calibrations is achieved by calibrating the wavelengths of lasers used in the inter-ferometers against national measurement standards of length, iodine-stabilised He-Ne lasers. Measuring devices for temperature, humidity and pressure used in the interferometers are calibrated in corresponding MIKES laboratories. The reliability of calibrations are verified by taking regularly part in international com-parisons.

Calibration servicesGauge block interferometers can be used to measure even other artefacts whose surfaces are flat and smooth enough; for instance to determine the ther-mal expansion coefficient of ceramic sealings and to measure the air gap between two parallel glass plates. Interferometric calibration sets also demands for gauge blocks: their end surfaces must be parallel, flat and without scratches. MIKES calibrates gauge blocks of grades K (00) and O and end standards, e.g. quartz metres, according to the following table.

Table 1. Calibration subjects and measurement uncertainties


Mass pressure flow



geometry Chemistry

Calibration of gauge blocksby mechanical comparison

Mechanical comparison measurement is the most common way to determine the length of a gauge block. In this method, the length of the gauge block under calibration is compared to the length of a calib-rated gauge block with same nominal length by using a specific comparator, Figure 1.

Gauge block measurementComparison measurements of gauge blocks that have the same nominal length and that are of the same material are simple, reliable, fast and inexpen-sive. The method is also applicable to gauge blocks whose surfaces have been wornout in use. MIKES calibrates steel, hard-metal, and ceramic gauge blocks in lengths 0.1....1000 mm (Table 1). In calibra-tion we check the flatness of the surfaces and remove splatters that could prevent reliable use of the gauge blocks. A regular inspection of gauge blocks prevents a possible damage to affect the whole set. The use of uncalibrated gauge blocks in production quality control and in calibration of measurement equipment causes extra risks and costs.

Measurement device Measurement range Uncertainty (k=2)Tesa gauge block comparator 0,1 mm …100 mm Q[0,050; 0,00087L] µmMIKES comparator for longgauge blocks

100 mm …1000 mm Q[0,20; 0,00087L] µm

L is the nominal length in millimeters

Table 1. Calibration of gauge blocks by mechanical comparison..

Figure 1. The sensor of the gauge block com-parator identifies the location of the surface by using 0.6 Nm measurement force.

Ilkka Raeluoto, Senior Research Technician, Tel +358 050 410 5562, [email protected]




Calibration of gauge blocks by mechanical comparison

Nominal length rangemm

Calibration gradeK

μm

Grade0

μm

Grade1

μm

Grade2

μmAlaraja Yläraja ±te tv ±te tv ±te tv ±te tv

0.5 10 0.20 0.05 0.12 0.10 0.20 0.16 0.45 0.30

10 25 0.30 0.05 0.14 0.10 0.30 0.16 0.60 0.30

25 50 0.40 0.06 0.20 0.10 0.40 0.18 0.80 0.30

50 75 0.50 0.06 0.25 0.12 0.50 0.18 1.00 0.35

75 100 0.60 0.07 0.30 0.12 0.60 0.20 1.20 0.35

100 150 0.80 0.08 0.40 0.14 0.80 0.20 1.60 0.40

150 200 1.00 0.09 0.50 0.16 1.00 0.25 2.00 0.40

200 250 1.20 0.10 0.60 0.16 1.20 0.25 2.40 0.45

250 300 1.40 0.10 0.70 0.18 1.40 0.25 2.80 0.50

300 400 1.80 0.12 0.90 0.20 1.80 0.30 3.60 0.50

400 500 2.20 0.14 1.10 0.25 2.20 0.35 4.40 0.60

500 600 2.60 0.16 1.30 0.25 2.60 0.40 5.00 0.70

600 700 3.00 0.18 1.50 0.30 3.00 0.45 6.00 0.70

700 800 3.40 0.20 1.70 0.30 3.40 0.50 6.50 0.80

800 900 3.80 0.20 1.90 0.35 3.80 0.50 7.50 0.90

900 1000 4.20 0.25 2.00 0.40 4.20 0.60 8.00 1.00

TraceabilityThe reference gauge blocks used in mechanical com-parison measurements are regularly calibrated using MIKES gauge block interfereometers. The waveleng-ths of lasers used in these interferometers are calib-rated by national measurement standard of length, iodine-stabilised He-Ne lasers.

Table 2. Accuracy grades of ISO 3650:1998 standard:.

Abbreviations in the table 2::

te = deviation of length from nominal lengthtv = variation in length

Note: The calibration ISO grades 0, 1, and 2 correspond to accuracy classes A, B, and C in OIML standard nr. 30, respectively.


Mass pressure flow



geometry Chemistry

2D- and 3D- measurement of form and surface roughnessBjörn Hemming, Senior Research Scientist, Tel +358 50 773 5744 [email protected]

Maksim Sphak, Researcher, Tel. +358 [email protected]”


The manufacturing tolerances of modern products and the aim to high quality require the ability to measure different form measurands of small artefacts having complicated shapes. Examples of such form measu-rands are straightness, parallelism, radius of curvatu-re and surface roughness. MIKES measurement and calibration services using a computer controlled form and surface texture instrument provides one solution to these measurement problems.

Form measurementsThe form measurement instrument can detect form deviations even as small as 0.6 nm. Examples of typi-cal form measurements are accurate measurements of straightness, inner and outer determinations of ra-diation of curvatures and diverse dimensional measu-rements of small artefacts (Figure 1). These include determinations of grooves lengths and depths and inner and outer angle measurements. The most im-portant technical specifications of the Taylor Hobson Form Talysurf instrument are gathered in table 1..

Figure 1. Straightness measurement on a cylindrical surface.


2D- and 3D- measurement of form and surface roughness

Ominaisuus Tiedot

Instrument and operational principle Taylor Hobson Form Taly-surf Ser. 2, Type 112/2815-02, inductive

Measurement tips Tdiamond tip, radius 0.002 mm; spherical sapphire tip, radius 0.397 mm

Measurement forces 1.0 mN (using diamond tip), 15-20 mN (sapphire tip)

Surface texture parameters R3y, R3z, Ra, Rc, Rda, Rdc, Rdq, RHSC, Rku, Rln, RLo, Rlq, Rmr, Rmr(c), Rp, RPc, Rq, RS, Rsk, RSm, Rt , Rv, RVo, Rz, Rz(JIS). In addition, a series of waviness parameters.

Longest measurement length 120 mm

Maximum height of artefact 700 mm, maximum width in 2D measurements is 50 mmLargest allowed from deviation 28 mm (120 mm arm)

Measurement speed 1 mm/sResolution 0.0006 µm

Lowest uncertainty Q[10; 70P] nm where P is the deviation from flatness in micrometers

Surface roughnessmeasurementsIn addition to calibration of surface roughness nor-mals, the surface texture instrument at MIKES is used for tasks related to quality control and product development. The surface roughness measurements at MIKES are based on the following standards: ISO 5436-1 and ISO 4287.

Measurement subjects• traceable calibration of surface roughness standards• divers measurements in development of prosthesis in health care industry• measurement of tribological samples• profile measurements of blades of excavation machinery• geometrical measurements in product development and quality control of electronic components• product development and quality control measurements of metal packings and components in hydraulics and pneumatics.

Taulukko 1. The most important technical specifications of the Taylor Hobson Form Talysurf instrument.

TraceabilityTraceability to the form measurement instrument comes from interferometrically calibrated gauge blocks, a line scale, an optical flat and a sphere.

Figure 2. Measurement of sideline.


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geometry Chemistry

Optical measurement of surface microstructuresVille Heikkinen, Researcher, Puh. +358 50 415 5980 [email protected]

Björn Hemming, Senior Research Scientist, Tel +358 50 773 5744 [email protected]

MIKES, Tekniikantie 1, 02150 EspooPuh. +358 20 722 111 www.mikes.fi

Micro to millimeter range structures can be measured at MIKES using scanning white light interference mi-croscope (SWLI).

The SWLI has sub-nm vertical and µm level horizon-tal resolution. It can measure square mm areas in a single scan. Benefit of SWLI compared to other instru-ments with similar vertical resolution include large measurement area ability to measure high steps and ability to measure overlapping surfaces inside of tran-sparent structures. See table 1 for more properties of the instrument.

Real life measurement uncertainty is case depen-dent and depends on measurement environment, properties of instrument and properties of measured sample. At MIKES we take care that the sample is clean, sample temperature is known, sample is well attached and properly aligned. Measurements are done traceably under consistent conditions and re-sults are well documented.

Figure 1. Bruker ContourGT-K Scanning white light interferometer

We do different measurementsusing the SWLI • different type of objects o surface shape measurements o x,y,z dimensions of details on surface o film thickness measurement, layer separation o surface roughness (2D and 3D ISO roughness parameters), flatness, deviation from a shape • calibration of different instruments • calibration of reference artefacts o step heights, air gap artefacts, film thickness artefacts • calibration of reference artefacts o step heights, air gap artefacts, film thickness artefacts

Examples of potential measured objects • Bearings, contact surfaces, surface topography and wear • Semiconductors and MEMS • Medical instruments and implants • Optical components • Precision machined components


Optical measurements of surface microstructures

Figure 2. Measurement of machined aluminium surface.

Table 1. Properties of SWLIProperty InformationOptical x-y resolutionPixel sizeVertical resolutionStep height measurement: • repeatability • accuracySample reflectivity:Maximum surface tilt (smooth samples):

3.8 – 0.7 µm7.2 – 0.2 µm < 0.1 nm

< 0.1 % < 0.75 % 0.05 % - 100 %3 ° (2.5× objective), 18.9 ° (20× objective)

Magnifications 2.5× and 20× objectives, 0.55×, 1× ja 2× zoom lensesMeasurement area (X × Y × Z mm3): smallest magnification largest magnification

3.5 × 4.6 × 3.5 0.4 × 0.6 × 3.5

Measurement area in pixels 640 × 480Programs Vision64 Analysis Software, MountainsMap, MatLabMaximum size of measured object 10 cm high × 20 cm wide, one dimension can be long

Ability to measure overlapping surfaces 2 surfaces in single measurementMaximum depth is dependent on refractive index, geometry and magnification, e.g. it is possible to measure through 0.3 mm thick glass 7 mm maximum depth limited by working distance

TraceabilitySWLI is traceable to SI-metre through MIKES’s own transfer stan-dards such as step height standards, gauge blocks and laser-in-terferometry.

Figure 3. Measurement of a groove on a glass surface.

Optimal measurement conditionSWLI is in underground measurement room with 20 ± 0,1 °C tem-perature. Most heat sources in the room have been eliminated by venting warm air out.


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Calibration of tachymeters

Jarkko Unkuri, Research Scientist, Tel +358 50 410 5506 [email protected]

Antti Lassila, Pricipal Metrologist, Tel +358 40 767 8584 [email protected]


MIKES calibrates angle and distance measurementsfunctions of tacheometers.

Calibration of a distance meter in a 30-metre measuring railReadings from a distance meter of a tachymeter is compared to readings from a laser interferometer of the 30 meter measuring rail. The measurement axis of the tachymeter and the laser interferometer are aligned to be parallel. The reading of the interfero-meter is set to zero at the beginning of the measuring rail. The observed reading of the distance meter at the zero point of the interferometer is subtracted from

Figure 1. MIKES 30-m measuring rail.

the readings of the distance meter. In the calibration certificate, the deviations from the references distan-ces and the expanded measurement uncertainty are given for each target point. The target point can be a prism, a reflector tape or a target plate. The measu-rement uncertainty depends on the scatter of the measurement results and is typically between 0.05 – 0.25 mm for accurate distance meters..


Calibration of tachymeters

Contents of tacheometer calibration Typical measurement uncertainty

calibration of length scaledeviation from reference precision target 0.15 mm spherical target 0.15 mm reflector tape 0.20 mm

without targetcalibration of angle scale

scale error of the vertical circle 2 - 3 ” scale error of the horizontal circle 1 - 2 “

tilting axis error 1 - 2 “

index error of the vertical circle 0.5 - 1.5 “

line-of-sight error 0.5 - 1.5 “

crosshair alignment and perpendicularity

influence of focussing

checking the readings of the environmental sensors

divergence test of automatic targeting

Calibration of angle measu-rements by using a rotary table and collimation tubesThe vertical and horizontal scales of a tachymeter are calibrated by using a Eimeldingen rotary table as a reference. The rotary table is calibrated using poly-gons and collimation tubes.

In the calibration of the horizontal scale, the tachy-meter is placed to the rotary table in such a way that the vertical axis is aligned to the rotational axis of the table (Figure 2). The table is rotated 360° in 30° steps and at each step the reading of the tachymeter that has been targeted to the collimation tube are recor-ded.

The vertical scale of the tachymeter is calibrated in the same way but now the rotary table is turned to vertical position by using optomechanics that have been designed especially for this purpose.

Figure 2. Calibration of the horizontal plane of a tachymeter in an Eimeldingen rotary table with a collimation tube as a target point.


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Angle and perpendicularity measurementsAsko Rantanen, Senior Research Technician, Tel +358 400 925 594 [email protected]


Angle measurements are important in all me-chanical engineering and construction industry. The significan-ce of angle measurements is increased also in dimen-sional measurements when dimensions increase. Per-pendicularity that is related to right angles and square blocks is an important special case of angle mesurement.

The SI-unit for angle is radian (rad) but depending on the branch of industry and the measurement subject other unist of angle are commonly used. In mecha-nical engineering angles are normally expressed in degrees [°], minutes [’] and seconds [”], in geodesy the most commonly used unit is gon (also referred to as grade) [gon]. In earth-moving work and for small angles the unit [mm/m] is generally used. The diverse group of units for angle include also the following ways to express the angle: percent [%] and length ratios.Perrpendicularity according to the ISO1101standard:

• As a result the width t of tolerance zone is given• One side is defined as the reference side and only against this side the perpendicularity is determined.

Figure 1. Polygon at-tached to a rotary table. Errors from the rotary table and the polyhed-ron can be separated by performing a measure-ment series using a Mol-ler Wedel HPR autocol-limator.



Angle and perpendicularity measurements

Instrument Measuring range

Measurement uncertainty (k=2)

Limitations

Optical polygons 0 ° - 360 ° 0.2 ”

Rotary indexing table 0 ° - 360 ° 0.5 ” indexing angle n x 15°Rotary table 0 ° - 360 ° 0.2 ”Autocollimator 0 ° - 1 ° 0.02 ”Electronic level 0 ° - 360 ° 0.2 ”

Theodolite 0 ° - 360 ° 0.2 ” instrument limitsthe vertical angle

Angle block 0 ° - 360 ° 0.2 ”

Steel or granite squares 90 ° 0.5 ” max. length 1 mCylinder square 90 ° 0.5 ” max. length 1 m

Optical right angle 90 ° 0.5 ”

Instruments for measuring angleThe most typical objects of calibration in mechanical workshops are rotary tables of machine tools and measuring machines, universal bevel proctractors, angle blocks, and different kinds of spirit (bubble) le-vels. Typical angle measurement instruments used in machine installation and in construction engineering are e.g. electronic levels, theodolites, levelling instru-ments, tacheometers, laser interferometers, autocolli-mators and polygons.

Figure 2. Calibration of the horizontal scale of a tacheome-ter using an Eimeldingen rotary table and an autocollimator as a target point.

Figure 3. Calibration of a granite square using a measuring machine developed at MIKES.

Table 1. Examples of lowest uncertainties for angle measurement instruments.

Measurement uncertaintyAll measurements are performed in a well-controlled laboratory room at temperature +20 °C ± 0.1°C. The achievable measurement uncertainty depends criti-cally on the artefact under calibration and its proper-ties (e.g. its form errors and surface roughness).


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Measurements of accurate inner and outer dimensions


Measurements using SIP length measuring machinePrecise measurements of inner and outer diameters are performed using SIP length measuring machine either by using its own scale or by referencing to a standard of equal length (Figure 2). In the measu-rement a contact is made using a ceramic spherical measuring probe, a flat tip or in inner measurements a lever probe. If the measurement depth in inner measurements is over 15 mm, special hook-shaped jaws are used. The measuring force can be tuned between 0.3…11 N. By measuring with several dif-ferent forces, the deformations due to the measuring forces can be eliminated from calculations and the result can be given at so-called zero-force. This is essential when the reference and the artefact under calibration are made of different materials or have

shapes. The accuracy of the length scale in SIP length measuring machine can be improved by using a laser interferometer (5528A) and a se-parate readout program. Measurements are per-formed in a well-controlled laboratory room at temperature + 20 °C ± 0.1 °C. Different types of heat sources are eliminated by using vent pipes, heat shields, and when necessary with a separa-te laminar flow. In addition to the measurement length, the measurement uncertainty depends on the measured artefact (shape and surface texture), on measuring instrument, measurement conditions, and on the method used.

In addition to diameter measurements, the SIP length measuring machine is used for thread measurements and tolerance comparisons. The inner threads are measured using spherical pro-bes and in outer thread measurements three wire method is used.

Ilkka Raeluoto, Senior Research Technician, Tel +358 50 410 5562, [email protected]


Figure 1. Measurement using SIP length measuring machine.


Measurements of accurate inner and outer dimensions

Measurement artefact Measurement uncertainty (k=2)

Thread plug 0 mm - 550 mm Q[0,2; 0,87L] µm

Ring gauge 1 mm - 500 mm Q[0,2; 0,87L] µmSphere 0.2 mm …200 mm Q[0,15; 0,7L] µm

L in metres

Measurements supplementing diameter measurements In order to get a precise picture of the features of an axially symmetrical artefact that is under measure-ment, one should also measure its roundness, sur-face roughness and straightness of sides using ap-propriate instruments.

TraceabilityMeasurements made using the SIP length measuring machine are traceable to corre-sponding transfer stan-dards that are calibrated at MIKES. The linear scale is calibrated using a laser interferometer, the reference gauge blocks are calibrated interferometrically, and the temperature sensors are calibrated in temperature baths against reference Pt25 thermocouples.

Figure 2. Mounting side by side the artefact under calibration and the reference in a comparison measurement.

Table 1. Measurement uncertainties achievable in diameter measurements.

Figure 3. SIP 550M length measuring machine.


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Coordinate measurement


Pasi Laukkanen, Research Engi-neer, Tel +358 50 382 9674, [email protected]


The coordinate measuring services at MIKES include measurements with an optical coordinate measuring machine and with a high-accuracy industrial size con-tact probe coordinate measuring machine.

Contacting coordinate measurement

The basic properties of MIKES coordinate measuring machine are accuracy, flexibility, speed, and automa-tic calculation of results.

Figure 1. Mitutoyo Legex coordinate measuring machine.

The MIKES 3D coordinate measuring machi-ne is a Mitutoyo Legex 9106 with portal struc-ture (Figure 1). Further information on this machine can be found in Table 1. The true measurement uncertainty is always case-spe-cific and depends on the environmental con-ditions, on the machine, and on the properties of the work piece. We pay special attention in our working on surface cleanliness, temperatu-re, mounting (Figure 2), alignment, measuring system, and on the documentation of results.


Coordinate measurement

Property Data

Performance checked according to ISO 10360-2:• maximum error in lengt-measurements• maximum 3D contact de-viation• maximum error in scanning-measurement

MPEe = (0.35 + L /1000) µm, L = mm

MPEP = 0.35 µm

MPEthp = 1.4 µm

Scales Mitutoyo Zerodur scales with floatingmounting, reolution 0.01 μm.

Travelling length X-910 mm, Y-1010 mm ja Z-610 mm

Contact probe Renishaw indexing head PH10MQ,Renishaw SP25M contact and scan-ning probe.

Software Mitotoyo COSMOS-software pakage • Geopak-Win geometry program• Statpak-Win geostatistical analysis for quality control• Scanpak-Win form measurement program 3Dtol-Win/MCAD300 comparison with CAD models and importing CAD data for programmingi

Measuring force 0.03 N…0.09 N

Maximum work piece mass 800 kg

Diameters of probes 0.5 mm…30 mm

The coordinate measuring machine is used for:

• pcustom measurements of 3D workpieces (Figure 3) and difficult shapes- scanning- digitizing of point clouds• various calibration of measurement devices- rulers, surface plates, gauges, cones,squares• calibration of transfer standards for coordinate machines- step gauges, ball cubes,

Optimal measurement conditions undergroundThe coordinate measuring machine is located in a large volume underground laboratory room held at + 20 °C ± 0.2 °C constant temperature. Most of the heat sources in the laboratory are eliminated using vent pipes. Moreover, the room is equipped with a 1000-kg load lifter on rails and a lift with 4000 kg ma-ximum load capacity can be used to haul the goods into the laboratory.tauksena (substitution method) .

JäljitettävyysIn commissioning, various laser and gauge block measurement were carried out on the coordinate measuring machine. Furthermore, the machine is regularly calibrated using our own measurement standards: step gauges, ball plates, and a laser interferometer. The measurement uncertainty and traceability are verified in each case separately using so-called substitute method, i.e. results are corrected using the results of a calibrated standard.

Figure 3. A typical artefact that can be measured using a coordinate measuring machine.

Table 1. The main properties of the coordinate measuring machine.

Figure 2. The proper mounting of work pieces is important.


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Optical coordinate measuring – vision measuring


Figure 1. The artefact under study can be illuminated with ring, coaxial or stage light.

The manufacturing tolerances of modern products and the aim for high quality require ability to make precise measurement of dimensional measurands on small artefacts of complicated shapes. The use of vision measuring machines and machine vision is wellestablished in non-contact high-precision measu-rement.

MIKES have a Mitutoyo Quickvision Hyper QV-350 vision measuring machine (optical CMM or video measuring machine) that is equipped with a CCD-ca-mera as well as with a contact probe. In non-contact optical measurements, the machine takes advantage of the measurement point location detected by the CCDcamera and location information from the preci-se scales attached to mechanical guides.sta.


Ville Byman, Research Scientist, Tel +358 50 386 9327, [email protected]


Optical coordinate measuring – vision measuring

Figure 2. A contact probe complements the vision measuring machine.

The machine is computer-controlled and measure-ments are fully automated. The machine is capab-le to measure length, diameter, angle, straightness, flatness, parallelism, and roundness.

The machine is especially suitable for measurements of circuit boards, thin-walled fragile plastic and metal-lic artefacts, and other artefacts that are inconvenient or impossible to measure with techniques using con-tact probes.

The artefact under study can be illuminated with ring, coaxial or stage light. There are four controllable seg-ments in the ring light and its height can be adjusted.

MIKES provides precise optical and contact dimensi-onal measurements tailored according to customers’ needs. Depending on the work order a calibration certificate or a field log is provided.

Property DataMeasuring volume 350 mm x 350 mm x 150 mmSize of the bench 490 mm x 550 mmMaximum work piece mass 15 kgLowest measurement uncer-tainty (k=2) , optical mode

U1XY = (0.8 + 2 L/1000) µm *U2XY = (1.4 + 3 L/1000) µm *U1Z = (3 + 2 L/1000) µm *

Lowest measurement uncer-tainty (k=2) , contact probe

U1XY = (1.8 + 2 L/1000) µm *

Maximum speed (rapid travel) 100 mm/sMMaximum acceleration 490 mm/s2

* L is length in mm. U1 is uncertainty along to one axel and U2 along two axels.

Table 1. Properties of the vision measuring machine.


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Jarkko Unkuri, Researcher, Tel +358 50 410 5506 [email protected]

Antti Lassila, Pricipal Metrolo-gist, Tel +358 40 767 8584 [email protected]


Calibration services at interferometric measuring rails

Line scale interferometer

MIKES calibration equipment for precision line scales allows calibration of up to 1.12-m long line scales with best possible accuracy. The measuring instrument is located in an air-conditioned laboratory room in which the tem-perature is held at + 20 ± 0.05 °C and the relative humidity at 45±5 %. The instrument performs computer-controlled measurements of distances between the graduation lines using a micro-scope equipped with a CCD camera for line detection and a Michelson interferometer for position measurement of the microscope. The line scales are supported at Airy points which minimizes bendings. The refractive in-dex of air is calculated from the measured air tempe-rature, pressure and humidity data by using updated Edlen’s equation. Thermal expansion is corrected to 20 °C using material temperature measured with four Pt100 sensors attached to the line scale. The gradua-tion line distances can be between 10 μm ... 1.12 m. The line scale interferometer is suitable for calibra-tions of me-tallic or glass graduated line scales.

Calibration of line scales and distan-ce meters

30-m measuring rail

MIKES 30-m measuring rail (Figure 2) offers good possibilities for calibration of precise length measuring devices. The temperature of the measurement room is kept at a + 20 °C ± 0.5 °C and the relative humidity at 45±5 %. The 30-m rail is realised using a highquali-ty linear motion guide and a movable measurement

carriage. A microscope, a CCD camera and a monitor used in line scale measurements are mounted on the carriage, The position of the microscope is measured using a laser interfereometer.

The temperature stability of the measurement room and precise gauges and sensors allow precise ther-mal expansion and refractive index of air compensati-on. The rail is suitable for calibration of various length standards. The calibrated devices can be physical artefacts like tapes and machinist scales or e.g. op-tical distance meters. Tapes and other flexible length standards are tensioned using a standardized force, a force given by the manufacturer or a force separa-tely agreed with customer. Most commonly a 50-Nm force of is used for tapes.

For thermal expansion compensation, a measured temperature and a coefficient given by the manufac-turer or by the customer are used.

Kuva 1. Piirtomittainterferometri.

Calibration of line scales and distance meters


Calibration of line scales and distance meters

Figure 2. 30-m measuring rail..

TraceabilityThe wavelengths of the lasers used in the line scale interferometer and in the 30-m measuring rail are calibrated using national measurement standard of length, iodine-stabilized He-Ne laser. The tempe-rature, pressure, and humidity sensors used in the measuring rail are calibrated at MIKES.

Device Measuringrange

Uncertainty (k=2)

Precision line scales, microscope scales

10 µm ... 1 m Q[6,2; 82L] nm**

Tapes, wires 0.001 m ... 30, (60, 90 ...) m

Q[35; 2L] µm

Machinist scales 0.001 m... 5 m Q[4; 1L] mm**Circometer 0.1 m ... 9,55 m

(diameter)Q[7; 2D] mm**

Plumb tapes 1 m ... 30, (60, 90) m

Q[250; 5L] mm**

Other devices 0 m ... 30 m (case dependent) L, D = measured length or corresponding diameter in meters*The uncertainty of calibration is usually larger than the afore-mentioned uncertainties due to the uncertainty resulting from the device to be calibrated.**Calculation of uncertainty Q[x; y]=(x2+y2)½

Table 1. Line scales, measuring ranges and measurement uncer-tainties..


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Ville Byman, Research Scientist, Tel +358 50 386 9327, [email protected]

MIKES, Tekniikantie 1,02150 Espoo +358 20 722 111 www.mikes.fi

Interferometric measurement of flatness and form

TasomaisuusThe surface structure and especially the flatness of the surface are important features of various com-ponents used in different areas of technology and physics. Examples of these include silicon wafers in semiconductor industry, sealing faces, bearing areas, contact surfaces in contact measurement methods, and surfaces of optical flats and lenses used for refle-cting and refracting light.

An optical flat is an easy to use transfer standard for flatness. In industry, optical flats are used, e.g. for

Figure 1. Calibration of an optical flat.

flatness measurements of gau ge blocks and contact surfaces of micrometer gauges. In these cases, the quality of the surfaces of optical flats is of essential importance for successful measurements of subject sur-faces. Moreover, optical flats are used to transfer flatness to interferometers measuring flatness and to other devices inspecting flatness in industry.

MIKES provides a measurement place for aforemen-tioned measurements and metrological traceability with its equipment for flatness and form measure-ments (Figure 1).



Interferometric measurement of flatness and form

Measurement methodThe measurement device for flatness at MIKES is a Fizeau interferometer that uses a He-Ne laser at wavelength 633nm as a light source. Interference frin-ges are obtained by adjusting a small angle between the reference plane and the plane to be measured. The shapes of the inter-ference fringes are analy-sed by using a so-called phase stepping method. As a result, one receives deviations of the plane under inspec-tion from the reference plane (Figure 2). The advantages of the method are speed, precision, and the fact that the entire measurement area is measu-red at once.

TraceabilityThe reference plane of the optical flat used in the inter-ferometer is of high-quality: deviations from a perfect plane are less than 20 nm. The reference plane is cal-culated either by using an absolute three-point met-hod or by comparing it to a liquid plane. Optical flats having different reflection coefficients are available which allows inspections of mirror surfaces as well as glass surfaces.

Measurement servicesThe MIKES equipment (Zygo GPi) can be used for surface profile measurements of objects that have diameters below 150 mm, best available measure-ment precision being 45 nm. A prerequi-site for such measurements is that the height variations of the arte-fact are less than 12 μm and slowly varying. As the method is based on interference of light and thus it is a non-contacting method it is also applicable for fragile materials. Moreover, it is applicable for very deman-ding measurement tasks due to its precision.

Figure 2. Examples of measured surface profiles of optical flats.


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Asko Rantanen, Senior Research Technician, Tel +358 400 925 594 [email protected]


Machine tool measurements

Machine tool measurementsDemands of production and quality systems require knowledge on the precision of machine tools. Different measurement are performed on machine tools during acceptance inspection, in connection with transfers, and when striving for preventive maintenance. MIKES provides its wide experience on dimensional and geo-metrical measurements, positioning and repeatabi-lity accuracy measurements, and measurements on machine tooled test work pieces.

The competent and experienced personnel of MIKES, modern equipment and continuous development of new measurement methods guarantee customers precise measurements performed according stan-dards. Figure 1. Scale measurement for a machine tool..

Figure 2. Setup for machine tool measurements.


Machine tool measurements

Geometrical measurementsGeometrical measurements are used for finding out the form defects in the most important organs of a machine tool and the mutual locations and positions of the organs. MIKES performs geometrical measu-rements according to ISO and DIN standards. The most important measurements subjects are: measu-rement of spindle runout, the parallelism between the spindle and the machine, perpendicularity measure-ments, and straightness and perpendicularity measu-rements of machine movements.

Positioning and repeatability accuracy measurementsSpindle positioning and repeatability measurements reveal errors at different points of the spindle. Errors in spindle movement can be compensated for by giving the compensation values to the control unit memory of the machine tool. The positioning measu-rement performed using MIKES laser interferometer is a fast and precise way to adjust the spindle move-ments of a machine (Figure 3). By using this method, the measurement precision is at its best below 0.001 mm/m.

Measurements on test work piecesMachine-tooling tests are used to find out the pre-cision of the machine in true machining circumstan-ces. MIKES geometrical measurements and measu-rements on work pieces made in machine-tooling tests complement each other. The work pieces are measured in a temperature-controlled laboratory room using versatile and modern measurement de-vices and methods. MIKES have a variety of the most common workshop measurement equipment and a selection of special tools (see Table 1). Figure 3. X-axis errors of a broaching machine before laser

measurement and adjustment and after.

Table 1. Devices used in machine tool measurements

TraceabilityAll measurement standards used in machine tool measureentsare calibrated using similar but more ac-curateMIKES transfer standards.

Geometrical andpositioning and

repeatability accuracymeasurements::

Measurements of test workpieces:

- laser interferometers - surface structure, form, roundness and length measuring machines

- autocollimators - iinductive sensors- electronic spirit level - common workshop measurement

devices- inductive sensors - coordinate measuring machine- plumb- other devices


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Measurement of roundness

Roundness in mechanical engineering industryApproximately 80 % of machined work pieces have elements with surfaces of revolution. Roundness has an important role for guaran-teeing faultless operation of machines and devices. This is even emphasized when reli-ability, longevity, low operating costs, and friendliness to the environmental are required.At MIKES we perform measurements of roundness on ring gauges, screw-plug gauges, slide bearings, metallic packings and hydraulic and pneumatic com-ponents. We also measure runout eccentricity, coa-xiality, parallelism and straightness (Figure 1).

Figure 1. Roundness measurement is an essential part of workshop manufacturing.


Veli-Pekka Esala, Senior Research scientist, Tel +358 40 866 [email protected]


Measurement of roundness

Measurement potentialRoundness is measured either by using a rotating spindle or using a roundness measurement instru-ment equipped with a rotating table. Measurements can be performed using several different filters accor-ding to the ISO 1101 standard’s definition (MZ) or other computing methods (MC, MI, and LS). The use of two alternative machines guarantees the customer that the artefacts can be measured properly and cost effectively. More information on the machines can be found in table 1.

Cylindricity is measured using a machine equipped with a rotating table (Figure 2), with almost the same settings also the following measurement can be per-formed: coaxiality, runout eccentricity, parallelism and straightness. Cylindricity measurements are a part of the calibration of ring gauges and screw-plug gauges.

TraceabilityTraceability to the sensors in both machines comes from magnification standards that are calibrated using MIKES form measurement instrument which in turn gets it traceability from gauge blocks calibrated using an interferometer. The guide bars and shafts in the machines are calibrated using error separation.

Model Rotatingpart

Maximumheight of

the artefact/ mm

Maximuminner/ outerdiameter ofthe artefact

/ mm

Maximummass of the

artefact/ kg

Other Expanded uncer-tainty(k=2)

Talyrond 73 HRroundness

spindle 400 175 / 300 100 surface can be discon-tinuous or asymmetrical

Q[0,01; 0,01R ] µm

Talyrond 262cylindricity

table 500 - / 350 50 surface can be disconti-nuous

Q[0,1; 0,5L] µm

R is the deviation from roundness in micrometers; L is the height of the cylinder in meters Q[x; y]=√(x2+y2)

Figure 2. Measurement instrument Talyrond 262 for roundness and cylindricity.

Table 1. MIKES roundness and cylindricity measurement instruments


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Calibration of microscpes and calibration standards

2], which can be calibrated at MIKES. 1-D and 2-D gratings are calibrated either by laser diffraction or by metrology atomic force microscope (MAFM). Pitch and orthogonality of the grid can be measured. Step height standards or z scale of 1-D or 2-D gratings can be calibrated.

[1] Guideline VDI/VDE 2656 Part 1 (Draft): Determination of geo-metric quantities by Scanning Probe Microscopes - Calibration of Measurement Systems

[2] V. Korpelainen and A. Lassila, Calibration of a commercial AFM: traceability for a coordinate system, Meas. Sci. Technol. 18 (2007) 395–403

Figure 1. MIKES interferometrically traceable metrology AFM (MIKES IT-MAFM).

Reliable measurement results in research, manufac-ture and quality control require knowledge of accu-racy of measurement intruments. Calibration is the best way to check the accuracy and stability of the instrument. The calibration can be done with calibrat-ed transfer standards. Official calibration certificate guarantees traceability to the definition of the metre.

For optical microscopes MIKES provides calibration of high quality line scales.

Scanning probe microscopes (SPMs) can be calib-rated using several kinds of transfer standards [1,

Virpi Korpelainen, Senior Research Scientist, Tel. +358 50 410 5504 [email protected]


Calibration of microscopes and calibration standards

Calibration itself gives information about the accu-racy of the instrument. Accuracy of the measurement can be increased by corrections of the errors dete-cted in the calibration either directly in the measure-ment software or after the measurement with sepa-rate software.

The first step in the calibration is measurement of x and y scale errors by 1-D or 2-D gratings and z scale errors by step height standards. The calib-ration of the x and y scales gives also information about the linearity of the scales. The linearity of the z scale needs to be checked by several different step height standards. Orthogonality errors can be detected by 2-D grids. Out-of-plane errors can be

measured using a flatness standard. In the most accurate calibrations also some other error types has to be measured and corrected; e.g. orthogo-nality of z axis, rotational and other guiding errors. There are also other error sources which should be taken into account, e.g. tip-sample interactions, vibrations, noise and thermal drift. Calibration period depends on the stability of the device, e.g. microscopes with open loop scanner need calibra-tion before and after each measurement.

Range Uncertainty1-D grid (diffraction measurement)

Pitch 300 nm - 10 µm 50 - 100 pm2-D grid (diffraction measurement)

Pitch 300 nm - 10 µm 50 - 100 pmOrthogonality

1-D grid (AFM measurement)Pitch, p 100 nm - 10 µm Q [3.4; 0.2 p/µm] nmOrthogonality 14 mradStep height, h 10 nm - 2 µm Q [2; 0.2 h/µm] nmFlatness 100 µm × 100 µm 5 nm

Step height standard 10 nm - 2 µm Q [2; 0.2 h/µm] nmFlatness standard 100 µm × 100 µm 5 nm

Table 1. Calibration services for SPM standards.

Figure 3. Some error types of SPMs.


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Length in geodesy

Finnish Geospatial Research Institute, FGIThe Finnish Geospatial Research Institute, FGI, of the National Land Survey of Finland maintains measure-ment standards for geodetic and photogrammetric measurements and is the National Standards La-boratory of acceleration of free fall and length. The FGI takes care of the fundamental measurements in Finnish cartography and of geographical information metrology and carries out scientific research in geo-desy, geographic information sciences, positioning, navigation, photogrammetry and remote sensing.

Calibration servicesThe FGI calibrates high precision electronic distance measurement (EDM) instruments, geodetic baselines and photogrammetric test fields. Moreover, we calib-rate precise levelling rods, digital and traditional, and system calibration of digital level instruments. The calibrations are performed in addition to the Masala laboratories at Nummela Standard Baseline and at Metsähovi Fundamental station. Most of our work is carried out in field conditions or conditions analogous to operating situations.

Figure 1 and 2. The Nummela standard baseline measured by using the Väisälä comparator has been one of the most accurate and stable lengths over the past half decade.

Markku Poutanen, Prof.,Tel. +358 29 531 4867,[email protected]

Finnish Geospatial Research Insti-tute, FGI, Geodeetinrinne 2, 02430 Masala,Tel. +358 29 530 1100, www.fgi.fi

Paavo Rouhiainen,Senior research scientist, Tel +358 29 531 [email protected]

Jorma Jokela, Research manager,Tel +358 29 531 [email protected]


Length in geodesy

Figure 4. Calibration of a digital precise level instrumentand system calibration of a barcode rod.

Traceability and uncertaintyNational measurement standards for length at the FGI are a Väisälä interference comparator with a quartz meter system and a levelling rod comparator system with a laser interferometer. All the measurements are traceable with a known uncertainty. Baselines (864 m and 432 m) measured with the Väisälä interference comparator have typically a measurement uncertainty ranging from 0.1 ppm to 0.2 ppm (k=2) and the measu-rement uncertainty for other baselines (1 m - 10 km) is at its best 0.2 ppm. The measurement uncertainty for calibration of levelling rods is 1 ppm and 5 ppm for calibration of levelling systems.

Figure 3. Calibration of the most accurate distance meters of the world can be done at the Nummela Standard Baseline. Nummela scale has been transferred also to several foreign baselines.

Figure 5. Research on the accuracy of GNSS antennas can be made at the test field of the Metsähovi observatory.

Research and developmentThe FGI carries out research and development on methods and equipment for the measurements for geodesy and geospatial information science. In addi-tion to length measurements, we perform other preci-sion measurement in surveying, e.g. measurements of angle, azimuths, determination of coordinates and satellite positioning. We also participate in GNSS metrology related projects. International cooperation is a central part of our work and we have measured baselines in about 20 countries.

80 — VTT MIKES METROLOGIA Kalibrointipalvelut 2016

Massa, paine ja virtaus

Lämpötila, kosteus

Sähkö, aika ja akustiikka Optiikka Pituus,

geometria Kemia

Water quality

ENVICAL SYKE is focusing on the research and development of metrology in chemistry. Our ac-tivities include development of accurate and traceable calibration methods, testing the reliabi-lity of new measurement techniques and validati-on of methods of analysis and quality assurance.

Traceable calibrationsThe SYKE accredited calibration laboratory (K054: EN ISO/IEC 17025) produces calibration results with high accuracy and traceability and is responsible for developing methods based on primary techniques.

In general, Isotope Dilution Mass Spectrometry (IDMS) can be regarded as one of the main referen-

Teemu Näykki, PhD, Associate Professor,Senior research scientistTel. +358 29 525 1471,[email protected]

Finnish Environment Institute Hakuninmaantie 6, 00430 Helsinki, Tel. +358 29 525 1000,www.syke.fi/envical/en

Timo Sara-Aho,Researcher,Tel. +358 29 525 [email protected]

ce methods for elemental analysis, and appropriately applied it offers the highest accuracy and smallest measurement uncertainty.

This method is used to measure the elemental content (usually mass fraction) of an unknown test sample, which has natural isotopic composition. This sample is mixed with another sample (spike) con-taining a known amount of the same element un-der investifgation. Isotopic composition of the spike sample is known and it is different from the isotopic composition of the test sample; usually such a way that the rarer isotopes of the element are enriched. When the test sample and the spike are completely mixed, the resulting mixture (blend) has a new (iso-tope diluted) isotopic composition, where the isoto-pe ratios are between the test sample and the spike

Photo Timo Vänni


Water quality

Quantity / method / object

Measurement range

CMC, Expressed as Expanded Uncer-

tainty (k=2) )Chemical analyses; amount of substance

Mass fraction of soluble total mercury (Hg) in syn-thetic water, fresh natural water (not sea water) and waste water

30 - 125 ng/kg >125 - 5 000 ng/kg

6 % 3 %

Mass fraction of soluble total lead (Pb) in synthetic water and fresh natural water (not sea water)

0,200 – 1,00 μg/kg >1,00 - 100 μg/kg

0,030 μg/kg 3 %

sample added. The isotope ratios of the mixture are measured and the result is directly proportional to the mass fraction or concentration of the element in the sample.

At present, the scope of SYKE’s calibration laborato-ry accreditation includes measurement of lead (Pb) in natural water and mercury (Hg) in natural and was-te water. The methods are based on the isotope dilu-tion inductively coupled plasma mass spectrometric (ICP-MS) technique. The range of measurements is being complemented with tests for dissolved oxygen and also nickel and cadmium, listed as priority subs-tances in the Water Framework Directive. The isoto-pe dilution mass spectrometric technique is widely utilized by SYKE also for measurement of organic chemical contaminants.

Our customer base consists of public and private parties requiring accurate and reliable measurement results for their environmental samples. For instan-ce, we have produced traceable reference values for proficiency tests (PTs).

Research ActivitiesThe comparability of the measurement results is inter-nationally very important. Reliability and comparability of the measurement results can be improved with the realistic measurement uncertainty estimation, valida-tion of the measurement methods, and ensuring the traceability of the measurement results.

ENVICAL SYKE is an experienced in research and development of the instrument’s reliability and procedures for measurement uncertainty estimation. We have constructed new tools for both laboratory measurements as well as for portable and continuous field water quality measuring devices to indicate and improve the reliability of the measurement results. Examples of these tools are MUkit- and AutoMUkit- measurement uncertainty calculation software.

We also actively participate in organizing proficiency tests for water quality sensor measurements.

In addition to maintenance of measurement stan-dards’ international traceability, our activities include national and international communication, publication, and training in the field of metrology. Upon request, we arrange customized training in the estimation of measurement uncertainties in chemical measure-ments or validation of analytical methods.

Table 1. CMC data..

Photo Timo Vänni

MIKES Tekniikantie 1 02150 ESPOO

MIKES-Kajaani Tehdakatu 15, Puristamo 9P19 87100 KAJAANI

Tel +358 20 722 111 email: [email protected]

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