instrumentation wk -1

7/31/2019 Instrumentation WK -1

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Dr. Shafiq R. Qureshi

PhD ( University of Manchester)

Engineering Sciences Department

ME-831: Instrumentations, Measurement& DAQ Systems


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Course Overview

Basic theory of Instrumentation and Experimentation

Computer based Data Acquisition - theoretical concepts

LABVIEW Programming and data acquisition

Process instrumentation

Assignments based on self study and presentations

LABVIEW Project

Quiz Assignment and Tests as per NUST Statue


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Books

Figliola, R.S. & Beasley, D.E., Theory & Design for Mechanical Measurements , J. Wiley & Sons, Inc. Availablein Library

Patrick F. Dunn, Measurement and Data analysis forengineering and science

Available in Library

Fundamentals of Instrumentation and Measurement editedby Dominique Placko

EBook Available


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Instrumentation comprises scientific activities and technologies thatare related to measurement. It is a link between physical, chemicaland biological phenomena and their perception by humans.

Measurement is the basis of scientific and industrial research. Itallows us to understand the phenomena we observe in ourenvironment by means of experimental deduction and verification

Measurement therefore brings together knowledge andtechnological progress.Universal and essential to many disciplines, it is, in fact,fundamental to most human activity.

INSTRUMENTATION AND MEASUREMENTS


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Terminologies

Measurement, Instrumentation and Metrology

The expression of measurement needs or tests are an everydayoccurrence in science and industry. All existing tools that help uscarry out measurement are part of instrumentation. Rules for usingand guaranteeing measurement created metrology. It is importantto point out that definitions of these related terms are sometimes

confused, as with measure and metrology.

The word measurement has many meanings. The InternationalVocabulary of Basic and General Terms in Metrology (VIM), usingInternational Organization for Standardization (ISO) norms, has

defined measurement as:a set of operations having the object of determining the value of aquantity

In other words, a measurement is the evaluation of a quantitymade aftercomparing it to a quantity of the same type which we use as aunit.


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Fig 1 Control and measurement system


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Metrology, the science and grammar of measurement isdefined as the field of knowledge concerned withmeasurement.

Metrology

It guarantees the meaning and validity of measurement by strictaccordance to established units. These units are standardized

on national and international levels.Metrology plays a role in international agreements joiningnational systems of measurement to those used in othercountries, making conversion between systems possible.

Standardized measurement units mean that scientific andeconomic figures can be understood, reproduced, and convertedwith a high degree of certitude.

Example : The International Bureau of Weights and Measuresbased in France is an international authority in charge of

establishing international metrological rules.


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In scientific research, interactions between experimentsand theories are permanent. Therefore, establishing acomparative relation between a quantity to be evaluated

and a reference quantity or standard by means of aninstrument of measurement is an interaction betweeninstrumentation and metrology that guarantees thereliability of obtained results.


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Experiments Need - Why do we need Experiments ?

Some quotes

Experiments are basis of all theoretical predictions, withoutexperiments there would be no results, and without anytangible data, there is no basis for any scientists orengineer to formulate a theory.

The advancements of culture, civilization depend uponexperiments which bring about new technology.

Making predictions can serve as a guide to what we expect,but to really learn and know what happens in reality,experiment must be done.


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The interplay betweenexperiment and theory.

In scientific method experiments are done in a systematic and

rigorous manner, with the goal of arriving at a broader theoreticalunderstanding. Using the approach the results of positiveexperiments and observations are gathered and considered.

A preliminary hypothesis is formed. All rival hypotheses are testedfor possible

validity. Hopefully, only one correct hypothesis remains


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Science and Experiment There are two goals of science: Explanation and understanding,

Prediction and control.

Its modern basis is the experimental method of proof.

Explanation and understanding encompass statements that makecausal connections.One example statement is that an increase in the temperature of aperfect gas under constant volume causes an increase in its pressure.

These usually lead to an algorithm or law that relates the variablesinvolved in the process under investigation.

Prediction and control establish correlations between variables. Foraboves example, these would result in the correlation betweenpressure and temperature.


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ExperimentsAn Experiment is an act in which one physically intervenes withthe process under investigation and records the results.

Traditionally theory explains existing results and predicts newresults; experiments validate existing theory and gather resultsfor refining theory

Some terminologies

Variables: Independent , Dependent and

extraneousAn experiment manipulates record effect on .Variable which

cannot be controlled

Controlled Experiment : in which all variable are identified andcontrolledIn reality all experiments have some extraneous variable and

Inability to precisely control every variable is the primarysource of a experimental uncertainty.


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Parameter : A variable that is either actively or passivelyfixed through out the experiment is called a parameter. i.e. Re in flow measurement

Classification of Experiments:

Variational : Establishes the mathematical relationship

between experiments variable. Ideal &imperfect

Validational : To validate a specific hypothesis Galilean experiment

Pedagogical : To teach the novice or demonstrate

Explorational: to explore the idea or possibility

Discovery : discovery of bacterial repression by penicillin


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Experimental Test Plan

Parameter Design Plan:

Test objective and identification of process variables and amean for their control.

System and Tolerance Design Plan:

This is selection a selection of a measurement technique,equipment and test procedure based on some preconceivedtolerance limit for error.

Data reduction Design plan:

Plan ahead how to analyze, present and use the anticipateddata


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Review different unit system at your own

Identify and understand seven fundamental dimension in SI and Technical English System

Conversion between both system

A quiz will follow next week

What is Significant Figure ?

It has something to do with precision of result ?

Most Significant, Least significant


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Definitions of Common Terms1. Readability of an InstrumentCloseness with which the scale of an instrument could be read

An instrument with a 12-in scale would have a higher readability than aninstrument with a 6-in scale and the same range.

2. Least CountSmallest difference between two indications that can be detected on theinstrument scale.

3. Sensitivity Analog InstrumentRatio of linear/angular movement of the pointer to the change in the measured

variable causing this movement.e.g., a 1mV recorder might have a 25cm scale length. Its sensitivity would be25cm/mV


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Definitions of Common Terms4. HysteresisAn instrument is said to exhibit hysteresis when there is a difference in readingsdepending on whether the value of the measured quantity is approached fromabove or below.

5. AccuracyIndicates the deviation of the reading from a known input.

6. PrecisionIndicates the ability of an instrument to reproduce a certain reading with a givenaccuracy.

Hysteresis may be the result of mechanical friction, magnetic effects, elasticdeformation, or thermal effects


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CalibrationIt is very important to reduce the errors in accuracy

Calibration MethodsCalibration procedures involve a comparison of the particular instrument witheither:

1. A primary standard

2. A secondary standard with a higher accuracy than the instrument tocalibrated3. A known input source

StandardsNIST maintains the standards in US

L: 1982 definition: 1m is the distance light travels in 1/299,792,458ths of a secon T: 1967 definition: The Thirteenth General Conference on Weights and Measures

adopted a definition of the second as the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levelsof the fundamental state of the atom of cesium-133. The estimated accuracyof this standard is 2 parts in 10 9 .

M: Defined in terms of a platinum-iridium mass maintained at Int. Bureau of Weights and Measures

V: 1990 definition: Related to Josephson effect which occurs at liquid heliutemperatures: Based on Quantum Hall Effect

Temperature: An absolute temperature scale was proposed by LordKelvin in 1854


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Standards


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Standards


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Standards


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Standards


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Assignment

Book: Theory and Design for MechanicalMeasurements

Chapter 8 Temperature measurementChapter 9 Pressure and velocity MeasurementChapter 10 Flow MeasurementChapter 11 Strain Measurement

Chapter 12 Metrology, Motion Force and PowerMeasurement


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Fluid Mechanical VariablesMeasurement

Pressure MeasurementBarometers and barographsBourdon tubes, Vidie capsules, MEMS

diaphragmsSound Pressure/Level Measurement

Human ear responseMicrophones

Moving coil

QuartzPiezoelectricElectretCapacitance


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Flow Measurement

Differential Pressure Flow meters Variable Area Flow meters Positive Displacement Flow meters Turbine and Vane Flow meters Impeller Flow meters Electromagnetic Flow meters Ultrasonic Flow meters

Vortex Shedding Flow meters Thermal Mass Flow meters Carioles Effect Mass Flow meters Drag Force Flow meters


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Point Velocity Measurement Pitot Probe Anemometry Thermal Anemometry Laser Anemometry

Viscosity MeasurementSurface Tension Measurement

Thermal Conductivity Measurement Heat Flux Measurement Calorimetry (e.g. differentialscanning calorimeter (DSC)) Thermal Imaging


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Temperature MeasurementSolid differential thermal expansion (e.g.bimetallic strips)Liquid expansion (e.g. glass bulb-capillary)

Gas/vapor expansion (e.g. refrigeratorsensor)Resistivity change (e.g. platinumresistance (RDT))

Thermocouples (e.g. Type K and J)

ThermistorsSemiconductor diodesInfrared sensorsPyroelectric sensors

Temperature indicating materials (e.g.battery tester strip)Resonating crystal sensors (e g quartz

Thermal Variables Measurement

instrumentation wk -1

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