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T E C H N I C A L M A N U A L

ELECTROCHEMICAL

QUARTZ CRYSTAL

NANOBALANCE

SYSTEM EQCN-900/F

ELCHEMAP.O. Box 5067

Potsdam, New York 13676www.elchema.net

Tel.: (315) 268-1605 FAX: (315) 268-1709

TABLE OF CONTENTS

1. INTRODUCTION ......................................................................................... 2

2. SPECIFICATIONS ........................................................................................ 4

3. CONTROLS .................................................................................................. 73.1. Front Panel ..................................................................................... 73.2. Back Panel ..................................................................................... 133.3. Faraday Cage: Side Panel ............................................................. 163.4. Faraday Cage: Internal Panel ........................................................ 19

4. OPERATING INSTRUCTIONS ................................................................... 214.1. Inspection ....................................................................................... 214.2. Precautions ..................................................................................... 214.3 Faraday Cage ................................................................................. 224.4. Grounding ...................................................................................... 224.5. Thermal Sensitivity ....................................................................... 23

5. INSTALLATION .......................................................................................... 245.1. Initial Set-up .................................................................................. 245.2. Power ON Checks .......................................................................... 265.3. Connections to a Potentiostat and Electrochemical Cell .............. 275.4. Testing Experiment with Real Cell ON .......................................... 285.5. Quartz Crystal Immittance Measurements .................................... 295.6. Other Utilities (Optional) .............................................................. 31

6. CRYSTAL-CELL ASSEMBLY ................................................................... 336.1. Mounting Quartz Crystals ............................................................. 336.2. Assembling Piezocells in ROTACELL holder ............................. 336.3. Disassembling Piezocells from ROTACELL holder .................... 346.4. Final Checks .................................................................................. 34

7. ELECTRICAL CIRCUITS .......................................................................... 35

8. SERVICING NOTES .................................................................................... 39

9. WARRANTY, SHIPPING DAMAGE, GENERAL .................................... 40

1. INTRODUCTION

1. INTRODUCTION

The Model EQCN-900F Electrochemical Quartz Crystal Nanobalance is a measurement system for monitoring extremely small variation in the mass of a metal working electrode. The system allows one also to record the quartz crystal immittance (QCI) characteristics using an external frequency sweep generator. The amplitude of the a.c. current flowing through the crystal and the a.c. voltage accross the crystal are provided for QCI measurements. The EQCN-900F System consists of a Model EQCN-900F Nanobalance Instrument, Model EQCN-900F-2 Faraday Cage, and Model EQCN-900-3 Remote Probe Unit.

The material of the working electrode is gold, unless otherwise ordered. The working electrode is in the form of a thin film, and is placed on one side of a quartz single crystal wafer which is sealed to the side opening in an electrochemical cell. The AT-cut quartz crystal oscillates in the shear mode at nominal 10 MHz frequency. Any change in the mass rigidly attached to the working electrode results in the change of the quartz crystal oscillation frequency. The frequency of the working quartz crystal is compared to the frequency of the standard reference quartz crystal. The frequency measurements are differential, i.e. the frequency of the reference crystal is subtracted from the frequency of the working crystal. The obtained frequency difference is then measured by a precision frequency counter and displayed on the front panel. The frequency difference is converted to a voltage signal, calibrated in Sauerbrey mass units (referred to as the effective mass) and output to an analog recorder, or analog-to-digital converter.

Typical processes leading to the frequency change which corresponds to the effective mass change at the working electrode are listed below:

adsorption/desorptionmetal/alloy platingsurface oxidationcorrosion and corrosion protectionetchingheterogeneous polymerizationion ingress to (or egress from) ion exchange filmsoxidation/reduction of conductive polymer filmsintercalation coadsorption and competitive adsorptionmoisture accumulation (from gaseous phase)etc.

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1. INTRODUCTION

With the Model EQCN-900F you can monitor time transients of the effective electrode mass in an electrochemical or non-electrochemical cell, filled with liquid or gas. You can also perform voltammetric experiments of any type, and monitor potential or current dependence of the effective electrode mass.

The resolution of the EQCN-900F is 0.1 Hz which corresponds approximately to 0.1 ng of the effective mass change. The short-term stability is mostly dependent on the state of the working electrode surface and purity of the solution. Usually, it is better than 5 Hz. The exceptional linearity of mass measurements extends up to 100 μg. The use of AT-cut quartz crystals reduces temperature coefficient to the minimum. Under normal circumstances, the effect of temperature can be neglected in the range near the room temperature. If a very high sensitivity or wide temperature range are required, it is recommended to use a thermostatted cell and Model EQCN-900-3B Remote Probe Unit with thermostatted reference oscillator, or Model EQCN-900-4 Remote Probe Unit with external reference quartz crystal.

To perform electrochemical measurements, a potentiostat may be required. We offer a line of potentiostats specially designed to work with oscillating quartz crystal electrodes. The Model PS-205B is a general purpose potentiostat/galvanostat with potential control from -8 to +8 V, rise time of 500 ns, and 0.05% accuracy. The Model PS-305 is a precision potentiostat/galvanostat, and Models PS-505 and PS-605 offer exceptionally low noise and high precision, as well as an extended potential range control (-10 to +10 V).

For computer controlled measurements, we recommend a Data Logger and Control System DAQ-616SC with 16-bit VOLTSCAN Real-Time Data Acquisition and Control. It includes powerful data processing and graphing capabilities designed specially for electrochemical applications using different voltammetric techniques.

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2. SPECIFICATIONS

2. SPECIFICATIONS

Measurement Functions(1) EQCN: Electrochemical Quartz Crystal Nanobalance,(2) QCI: Quartz Crystal Immittance measurements,(3) F/V-C: Frequency-to-Voltage Converter

OscillatorsWorking Oscillator WO (EQCN): .................................. - internal oscillator for external

QC (ca. 10 MHz);Reference Oscillator RO (EQCN): ................................ - internal (f = 10.000 MHz), or

- external (9.9 < f < 10.1 MHz), TTL/CMOS compatible;

Frequency Scanning Generator FSG (QCI): ................. - external (9.8 < f < 10.2 MHz), TTL/CMOS compatible;

Measurement RangesFrequency Difference (digital) ..................................... 0 to 500,000 HzFrequency Shift (analog) ............................................. -100.0 to +100.0 kHz,

-10.00 to +10.00 kHz,-1.000 to +1.000 kHz,-100.0 to +100.0 Hz

Frequency Shift Linearity ............................................ 0.02 % of reading + 0.05 % FS

Mass Change ............................................................... -100.0 to +100.0 μg,-10.00 to +10.00 μg,-1.000 to +1.000 μg,-100.0 to +100.0 ng

Mass Change Linearity ............................................... 0.02 % of reading + 0.05 % FSExtended Linearity ..................................................... 10 % over nominal rangeMass Change Sign ..................................................... + for fWO < fRO

- for fWO > fRO

(Δm > 0, mass increase)Overload Indicator ..................................................... ca. 3 % over nominal range

ResolutionFrequency Difference: ................................................ 0.1 Hz (analog)Mass Change: ............................................................. 0.1 ng (analog)

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2. SPECIFICATIONS

Measurement speedMass change: ................................................................ 30 s per point (max)

with Filter OFFFrequency shift: ............................................................ 30 s per point (max)

with Filter OFFIQC, VQC, : ................................................................ 20 ms per point

SensitivityQuartz Crystal a.c. Current Amplitude: 10 mA/V, 5 mA/V, 2 mA/V, 1mA/V,

0.5 mA/V, 0.2 mA/V, 0.1 mA/VQuartz Crystal a.c. Voltage Amplitude: ........................ 200 mV (constant)Phase Detector Output (φ, PD-OUT): ........................... 45 deg/V

(i.e. -90 deg -2 V, +90 deg +2 V)

Calibration:IQC, φ: ............................................................. softwareVQC, m, f: ........................................................ hardware

Voltage to Mass Change Ratio: ................................... 10 V per nominal range (Mass mode)Voltage to Frequency Shift Ratio: ............................... 10 V per nominal range (Frequency mode)

RANGE MASS CHANGE FREQUENCY SHIFT(μg or kHz) 100.0 0.100 V/μg 0.100 V/kHz 10.00 1.000 V/μg 1.000 V/kHz 1.000 10.00 V/μg 10.00 V/kHz 0.100 100.0 mV/ng 100.0 mV/Hz

Mass and Frequency Shift:Extended linearity: ......................................... 10 % over nominal rangeOffsets:

coarse: ............................................... 0 to 90 μg or 90 kHz (approx.)fine: ................................................... 0 to 900 ng or 900 Hz (approx.)

Calibration: .................................................... hardware

Recorder OutputsAnalog Output Voltage Ranges:

Mass Change (V-OUT): .................................. -10 to +10 V (MASS output mode)Frequency Shift (V-OUT): ............................. -10 to +10 V (FREQUENCY output mode)

(note: DAQ-616 accepts 10 V inputs)Quartz Crystal a.c. Current (IQC-OUT): ......... -3 to +3 V (1 V/dB)Quartz Crystal a.c. Voltage (VQC-OUT): ....... 0 to +200 mV (constant)Phase Shift (, PD-OUT): ................................. -3 to +3 V

Offsets:Mass Change: ................................................ 0 or variable (0 to ca. 900 ng)

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2. SPECIFICATIONS

Frequency Shift: ............................................ 0 or variable (0 to ca. 900 Hz)Quartz Crystal a.c. Current (iQC-OUT): ........ softwareQuartz Crystal a.c. Voltage (VQC-OUT): ...... 0 VPhase Shift (PD-OUT): ................................. software

Calibration:IQC, φ: ........................................................... softwareVQC, Δm, Δf: .................................................. hardware

Operating ParametersWorking QC Resonator Frequency: ........................... 10 MHz bandReference Crystal Frequency: ..................................... 10.000 MHz (internal),

9.9 to 10.1 MHz (external, TTL/CMOS)Power Supply: ............................................................. 110/220 V, 50 - 60 HzDimensions: Instrument ........................................ 4.5H x 14.5W x 15D, inch

Faraday Cage ............................. ...... 14H x 12W x 11D, inch

Typical Measurement System Components

Model EQCN-900F Electrochemical Quartz Crystal Nanobalance InstrumentModel EQCN-900F-2 Faraday CageModel EQCN-900-3 Remote Probe Unit (mounted on back of Faraday Cage)Model EQCN-906 Frequency Scanning GeneratorModel DAQ-616SC Data Logger and Control Processor SystemModel PS-605E Potentiostat/GalvanostatModel RTC-100 Rotacell Cell System

Other Options

Model EQCN-900-3B Remote Probe Unit with thermostatted reference oscillator option (mounted on back of Faraday Cage)

Model RTC-100/T ROTACELL Cell System with ThermostatModel THERM-3 Temperature Controller Model TSR-100 Temperature Probe (solid state, teflon coated)Model STIR-2 StirrerModel FG-806 External Frequency Reference (9.9-10.2 MHz)Model FC-299 Frequency Meter/Calibrator/Generator (0.1 Hz to 60 kHz)Model PS-205B General Purpose Potentiostat/GalvanostatElectrodes Wide selection of quartz crystal working electrodes with Ag, Au, Al, Cr, Cu,

Fe, Ni, Pt, and Zn coatings

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3. CONTROLS

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3. CONTROLS

3. CONTROLS

The front and back view of the Instrument are presented in Figures 1 and 2, respectively. The side panel of the Remote Probe Unit is depicted in Figure 3 and the inside panel of the Faraday Cage is shown in Figure 4.

Read this Chapter carefully since it provides you with a full and systematic description of the functionality and limitations of all features and facilities available in the instrument. For exemplary schematics of connections and experimental measurement set-up, refer to Chapter 5.

3.1 FRONT PANEL

Controls for the front panel are described in the following order:

Switches Adjustable Potentiometers Panel Meters Diode Indicators Other Controls

Switches

1. QCI Toggle switch controlling power supplies to the QCI subsystem. To perform QCI measurements, set the QCI switch ON and allow 15 minutes to warm up and stabilize the temperature. Then, set the MODE switch (see: below) to the QCI measurements. When doing EQCN measurements, it is recommended to set the QCI switch OFF to achieve a better temperature stability.

2. MODE Toggle switch with two positions:EQCN - for Electrochemical Quartz Crystal Nanobalance measurements.

In the EQCN mode, the frequency displayed on the FREQUENCY (ΔF) panel meter corresponds to the difference between the frequency of the EQCN working oscillator and the reference oscillator (either the one sealed inside the Remote Probe Unit or an external reference oscillator).

QCI - for Quartz Crystal Immittance measurements

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3. CONTROLS

ELCHEMAF

Figure 1. Front panel view of the Model EQCN-900F Electrochemical Quartz Crystal Nanobalance with immittance measurement unit (QCI).

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3. CONTROLS

In the QCI mode, the external scanning generator output connected to the Faraday Cage F-SCAN input is enabled and the working oscillator WO used for EQCN measurements is disabled.

3. ATTENUATIONRotary switch for selection of the a.c. current range for a.c. current flowing through the quartz crystal under test in QCI measurements. The range selection has no effect on the EQCN oscillator. The ATTENUATION from 10 to 0.1 can be selected. This is an initial attenuation and it is automatically adjusted during measurements. For our standard laboratory crystals (QC-10-xx series) in air, the initial attenuation of 10 should be used. The same crystals in solution present much higher resistance at the resonance so that a higher gain is necessary, for instance you can use the ATTENUATION of 0.2. The frequency scanning should not be too fast, as this can generate an excessive noise on the IQC output. The frequency scan time of 60 seconds is recommended (it is set by QCI software and the Data Logger on the FSCAN page). If necessary, you can additionally use an external filter, e.g. ELCHEMA 3-Channel Tunable Filter, Model FLT-03, or perform digital smoothing using Data/Smooth utility in QCI 2.0.

4. POLARITYTwo position toggle switch to select the sign of the voltage signal representing the mass change. The importance of the sign change can be realized by considering the following relationships.

When the working crystal frequency is lower than the reference crystal frequency, the mass increase is manifested by the increase in the measured frequency difference. In this situation, the '+' sign should be selected to have the recorder output voltage V-OUT increasing with the electrode mass increase.

When the working crystal frequency is higher than the reference crystal frequency, the mass increase is manifested by the decrease in the measured frequency difference. In this situation, the '-' sign should be selected to have the recorder output voltage V-OUT increasing with the electrode mass increasing.

5. OFFSET Toggle switch to turn the offset for MASS or FREQUENCY in EQCN measurements ON or OFF.

6. FUNCTIONOUTPUT FUNCTION toggle switch with two positions:MASS - for conversion of frequency difference signal Δfac (which is an a.c. signal) to

the apparent mass change signal VΔm (which is an analog dc voltage signal). The VΔm voltage is scaled in mass units (10 V per nominal mass RANGE). The VΔm

signal is displayed on the Mass/Frequency METER and is also available at the V-OUT BNC socket on the back panel of the instrument when the MASS output mode is selected. The VΔm signal can be used to monitor apparent mass changes during experiments when the EQCN mode and MASS output mode are used. The output voltage range at the V-OUT BNC output is 10 V.

FREQUENCY - for conversion of frequency difference signal Δfac (an a.c. signal) to the analog dc voltage VΔf proportional to the frequency of the Δfac signal. The VΔf

voltage is displayed on the Mass/Frequency METER in V-OUT mode and is also available at the V-OUT BNC socket on the back panel of the instrument when

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3. CONTROLS

the FREQUENCY output mode is selected. The VΔf signal is scaled to have a sensitivity of 10 V per nominal frequency shift RANGE and can be used to monitor the frequency shift related to apparent mass changes and/or changes in viscoelastic properties of a solution and an electrode film during experiments when the EQCN mode and FREQUENCY output mode are used. The output voltage range at the V-OUT BNC output is 10 V.

7. V-OUT RANGERANGE selector for the F/V-Convertor. This is a four position rotary switch for the range selection, from 100 to 0.1 μg, or 100 to 0.1 kHz FS, depending on the output FUNCTION switch setting, MASS or FREQUENCY, respectively. The range selected is indicated by a lighting diode. For each range, the extended linearity from -110% to +110% of the range value can be utilized.

Adjustable Potentiometers

8-9. OFFSETTwo multiturn precision low-noise potentiometers marked COARSE and FINE for precision offset of the amplified mass signals. An exact zero offset can be obtained by setting the OFFSET toggle switch OFF. When the OFFSET toggle switch is ON, the zero offset can be obtained by turning both potentiometers clockwise until a resistance is felt (with the POLARITY switch in '+' position). Set a zero mass on the 100 μg first, then increase the sensitivity by switching to the 10 μg range and re-adjust the FINE offset knob position. Apply the same procedure on more sensitive mass ranges, if necessary.

In the EQCN measurements, usually the offset is not set to zero (that is: Δm = 0 on the Mass METER, with the crystal disconnected) but rather the offset is adjusted (to whatever value) to have a zero mass reading on the Mass METER with the crystal connected to the internal EQCN oscillator. This allows the experimenter to increase the mass sensitivity to the level otherwise impossible to attain. Usually, the mass is adjusted (offset) to zero just before recording the experimental mass-potential curve, or a mass-time transient. This is because in the EQCN technique we do not measure the absolute mass of the electrode but rather the mass change during the experiment. It is therefore convenient to start the experiment from a zero mass reading.

Panel Meters

10. ΔF FREQUENCY DPMDigital Panel Meter displaying, in Hz, the frequency difference between the frequency of the working quartz crystal and the frequency of a reference oscillator

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3. CONTROLS

(either the internal reference oscillator or an external TTL/CMOS reference oscillator).

11. METER Digital Panel Meter displaying the mass change or frequency shift depending on the output FUNCTION setting. When the FUNCTION toggle switch is set to MASS, the apparent mass change of the QC electrode is displayed and this switch is set to FREQUENCY, the frequency shift of the QC electrode is displayed.

Usually, the mass reading is adjusted (using OFFSET knobs) to zero just before recording the experimental mass-potential curve, or a mass-time transient. This is because in the EQCN technique we do not measure the absolute mass of the electrode but rather the mass change during the experiment. Similar concerns the frequency shift See also how the POLARITY switch affects the mass readings.

The DPM displays values in the range from -1000 to +1000 and includes decimal point dependent on the range selected. The extended linearity is 10 % over the nominal range. The overload diode is activated when the measured values exceed the range by ca. 3 %.

Diode Indicators

12. OVERLOADRed LED activated when the measured mass change (frequency shift) exceeds the actual V-OUT RANGE by ca. 3 %.

13. ATTENUATION INDICATORSGreen LED's indicating the iQC sensitivity selection.

14. FILTER INDICATORSGreen LED's indicating the FILTER selection. When all of the indicators are off, the filter is disconnected. The time constant of the filter increases from left to right (10 ms to 1000 ms).

15. MASS RANGE INDICATORSGreen LED's indicating the MASS RANGE selection.

Other Controls

16. FILTERThe FILTER selector switch which controls a filter damping the noise on the output voltage at the recorder V-OUT BNC socket on the back panel of the Instrument. Use a setting which works best for the particular experiment you are doing. Make sure that the damping acts only on the high frequency noise and not on the (slower) signal. Usually, the first or second setting, from the top, is appropriate. The filter time

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3. CONTROLS

constants increase, from top to bottom, in the following order: 10, 40, 80, 200, 1000 ms. When all FILTER indicators are off, the filter is disconnected.

17. POWERMain power switch. The switch is illuminated when the POWER is ON.

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3. CONTROLS

3.2. BACK PANEL1. ΔF-IN BNC socket for connection to the socket marked ΔF-OUT on the side panel of the

Faraday Cage. This connection is necessary in the EQCN mode. Optionally, it may also be utilized to perform a precision F-to-V conversion, e.g. to convert frequency of an external source, up to 100 kHz, to a DC voltage proportional to the input frequency. The DC voltage is output to V-OUT and is also displayed on the METER DPM. The input signal should have an amplitude 0.1 to 2.5 V ( i.e. 0.2-5.0 Vp-p) and the FUNCTION toggle switch should be in FREQUENCY position.

2. V-OUT BNC output socket providing voltage signals corresponding to:(a) relative apparent mass change of rigidly attached film to the EQCN working quartz crystal (for the FUNCTION switch in the MASS position);(b) frequency shift corresponding to the mass change or any change in visoelastic or other properties of the solution or films on the quartz crystal (for the FUNCTION switch in the FREQUENCY position).

3. IQC BNC output socket providing a rough analog voltage signal representing the current flowing through the quartz crystal under test in the QCI measurements. This output signal is offset and calibrated by the Data Logger under QCI 2.0 software and converted to the admittance modulus |Y|, conductance G, susceptance B, log|Y|, etc. utilizing VQC and PD functions.

4. VQC BNC output socket providing an analog voltage signal equal to the amplitude of the a.c. voltage across the quartz crystal under test in QCI measurements. This signal is constant (100 to 300 mV, typically: 200 mV).

5. PD, BNC output socket providing output from digital Phase Detector. The analog voltage signal is from -2 to +2 V for phase shift of +90o to -90o (±3.5 V max), i.e. the sign is reversed. After offset and calibration by the Data Logger, the signal has the sensitivity of 45 deg/V and zero offset (-2 V corresponding to -90 deg and +2 V corresponding to +90 deg). At frequencies lower than the resonance frequency, the phase shift is positive (the current is leading the voltage). At the resonance, the phase shift passes through zero and becomes negative (the current is lagging the voltage). At the anti-resonance, the phase shift again passes through zero and becomes positive. The phase detector output may have a higher uncertainty when the QC current has a very low value, e.g. near the anti-resonance.

6. I/O Standard female DB-25 socket for input/output communication. It should be connected to the corresponding male DB-25 connector on the side panel of the Faraday Cage.

7. SPLY 8-pin audio-type connector with DC supplies for the Remote Probe Unit. This socket should be connected to the corresponding socket on the side panel of the Faraday Cage.

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3. CONTROLS

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3. CONTROLS

8. GND Black or brown isolated Banana socket connected to the analog ground of the instrument circuitry. The analog ground is floating, i.e. it is not connected directly to the instrument CHASSIS or to the power line ground wire. You can connect externally the GND socket to the instrument CHASSIS or analog ground of other instruments, if necessary.

9. CHASSISBanana socket shorted to the instrument chassis. The instrument chassis is connected internally to the power line ground wire (a.c. ground). You can use this socket for reference purposes or to provide grounding for other instruments, if necessary.

10. POWER socketHP type socket for A.C. power inlet. It will accept 110 V or 220 V, 50 to 60 Hz. If the 110/220 V switch is not set properly for your power supply voltage, remove the power cord from the instrument and change the position of the 110/220 V selector to the appropriate position. Use power cords supplied with the instrument. American, British, and European power cords are available.

11. 110/220 V switchPower line voltage selector. The switch is set to 110 V when shipped within the USA and Japan, and 220 V, elsewhere. Check the position of this switch before you connect power to the instrument.

WARNING: Make sure the power in the instrument is OFF and power cord removed from the instrument before you change the position of the 110/200 V switch.

12. FUSE Power fuse. Use 250 V, 2 A slow melting fuse if replacement is necessary.WARNING: Make sure the power in the instrument is OFF, and the power cord is disconnected from the instrument before you replace the fuse.

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3. CONTROLS

3.3. Faraday Cage: Side Panel (Remote Probe Unit)

The following controls and connectors are located on the side panel of the Remote Probe Unit which is factory mounted on the back of the Faraday Cage.

1. RE BNC socket for connection to the Reference Electrode input in your potentiostat. Make sure that the shield of this cable is connected to the a.c. ground.

2. CE BNC socket for connection to the Counter Electrode output in your potentiostat. Make sure that the shield of this cable is grounded to the a.c. ground.

3. WE BNC socket for connection to the Working Electrode input in your potentiostat. Make sure that the shield of this cable is connected to the a.c. ground. For best noise reduction, the working electrode should be at the ground potential (either virtual ground or shorted to GND).

4. F-SCAN INBNC input socket for connection to a Frequency Scanning Generator, e.g. ELCHEMA FG-906S providing a TTL/CMOS compatible squarewave with frequency scanned in the range from ca. 9.5 to 10.1 MHz. This connection is necessary only in the QCI mode. The TTL/CMOS compatibility means that the signal amplitude is 5 V and voltage levels are 0 and +5 V. The generator must be able to provide 50 mA current without any change in the voltage amplitude. The rise time and fall time should be on the order of 5 ns or shorter. The generator should have an exceptional frequency stability (DDS with oven stabilized oscillator is a must).

5. EXT.REF. INBNC input socket for connection to a stable frequency source, e.g. ELCHEMA FG-806 providing a TTL/CMOS compatible square wave with frequency set in the range from ca. 9.9 to 10.1 MHz. This connection is only necessary if you want to use an external reference frequency instead of the internal frequency reference. The external frequency standard is to be utilized in the EQCN measurement mode. The TTL/CMOS compatibility means that the signal amplitude is 5 V and voltage levels are 0 and +5 V. The generator must be able to provide 50 mA current without any change in the voltage amplitude. The rise time and fall time should be on the order of 5 ns or shorter. The generator should have exceptionally good frequency stability (for FG-806 it is 0.001 ppm, or 10-7 %).

6. ΔF-OUTBNC output socket providing a frequency difference signal ΔF which is a.c. sine signal with voltage amplitude of 200 mV and frequency equal to the difference between the working oscillator frequency FWO and the reference oscillator frequency FRO . The ΔF-OUT should be connected to the ΔF-IN BNC input on the back panel of the Nanobalance Instrument EQCN-900F.

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RE

CE

WE

F-SCANIN

IN

F-out

F-OUT

INT.OSC.

EXT.

EXT. REF.

GNDFloat.

SPLY

1

2

3

4

8

9 5

6

10

7

12I/O

11

INT.

EXT.

F-REF

3. CONTROLS

Figure 3. View of side panel of the Faraday Cage.

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3. CONTROLS

7. F-OUT BNC output socket providing a high frequency signal fWO, fRO, or fEXT.REF selected by the F-OUT three-position toggle switch. The signal is TTL/CMOS compatible (0 to +5 V, ca. 10 MHz) and can be viewed on an external oscilloscope or its frequency measured using an external high frequency counter.

8. FLOAT/GND toggleToggle switch to select a floating or grounded EQCN working oscillator. When EQCN is used with potentiostat, the working electrode should be maintained on the ground potential by the potentiostat and the FLOAT/GND toggle should be set to FLOATING. When the potentiostat is not used, the FLOAT/GND toggle can be set to GND. The Faraday Cage chassis may also be connected to the a.c. GND if necessary.

9. F-REF toggleToggle switch to select either an Internal Reference Oscillator (INT) or an External Reference Oscillator (EXT) as the frequency reference for Δf measurements.

10. F-OUT toggleThree-position toggle switch to select frequency for output at the BNC output socket marked F-OUT. The selected frequency can be: a Working Oscillator (OSC.) frequency, an Internal Reference (REF.) frequency, or an External Reference (EXT.) frequency.

11. I/O Standard male DB-25 socket for input/output communication. It should be connected to the corresponding female DB-25 connector on the back panel of the Nanobalance Instrument.

12. SPLY 8-pin audio-type connector for DC supplies for the Remote Probe Unit. This socket should be connected to the corresponding socket on the back panel of the Nanobalance Instrument.

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3. CONTROLS

3.4. Faraday Cage: Internal Panel

1. REF REFERENCE ELECTRODE yellow pin tip banana jack for connection to the reference electrode (e.g., saturated calomel electrode, SCE, or a double-junction silver/silver chloride electrode, Ag/AgCl) for experiments involving a potentiostat. Use as short a wire as possible.

2. CE COUNTER ELECTRODE red pin tip banana jack for connection to the counter electrode (auxiliary electrode) in the electrochemical cell for experiments involving a potentiostat. Use a short wire for the connection.

3. AIR (EQCN)White pin tip banana socket for connection to the electrode exposed to air in the EQCN cell assembly. Use this socket for EQCN measurements only. The MODE switch on the front panel of the Nanobalance Instrument must be set to EQCN.

4. SLN (EQCN)Blue pin tip banana socket for connection to the EQCN electrode immersed in the solution. This is a connection to your working electrode deposited on the quartz crystal. Use this socket for EQCN measurements only. The MODE switch on the front panel of the Nanobalance Instrument must be set to EQCN.

5. AIR (QCI)White pin tip banana socket for connection to the quartz crystal electrode exposed to air. Use this socket for QCI measurements only. The MODE switch on the front panel of the Nanobalance Instrument must be set to QCI. This socket is not connected to the AIR (EQCN) white jack (3).

6. SLN (QCI)Blue pin tip banana socket for connection to the quartz crystal electrode immersed in the solution. This is a connection to your working electrode (the sensor) deposited on the quartz crystal. Use this socket for QCI measurements only. The MODE switch on the front panel of the Nanobalance Instrument must be set to QCI. This socket is not connected to the working electrode input of the potentiostat. It is also not connected to the LIQUID (EQCN) blue jack (6). Note that the QC inputs (5) and (6) are optically isolated from the frequency scanning generator (F-SCAN IN) input on the side panel of the Faraday Cage (Remote Probe Unit) and have no galvanic connection to it.

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3. CONTROLS

Figure 4. View of the inside panel of the Faraday Cage.

AIR

AIR

SOLN

SOLN

EQCN

QCI

3

REF

CE

1

2

4

56

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4. OPERATING INSTRUCTIONS


4.1. INSPECTION

After the instrument is unpacked, the instrument should be carefully inspected for damage received in transit. If any shipping damage is found, follow the procedure outlined in the "Claim for Damage in Shipment" section at the end of this Manual.

4.2. PRECAUTIONS

Care should be taken when making any connections to the instrument. Use the guidelines for maximum voltage at the inputs. There should be no signal applied to the inputs when the instrument is turned off. The outputs should not be loaded. They can only be connected to high input impedance devices such as plotters or oscilloscopes.

Use minimal force when putting on, or taking off, the BNC connections, otherwise they might become loose. Push the BNC forward when making a connection or a disconnection in order to relieve the rotational tension on the BNC socket.

Observe the color codes when connecting the power to the probe unit.

Operate the instrument in a cool and well ventilated environment.

Contact us in the event that any of our components do not operate properly. Our components are marked with seals. DO NOT try to open and fix anything yourself, otherwise your warranty agreement will be nullified.

22


4.3. FARADAY CAGE

The Faraday cage tips over easily. It is also possible for someone to accidently brush against it and break, or spill the contents of the cell inside. Hence, it is recommended to secure the Faraday cage if necessary.

4.4. GROUNDING AND INTERFERENCES

It is very important to properly ground the Nanobalance system. The circuitry operates at a high frequency of 10 MHz and is very susceptible to electromagnetic radiation and interference present in the surroundings. Since the working oscillator can not be enclosed in a case due the nature of measurements, the use of a Faraday cage is necessary. Usually, the door of the Faraday cage does not need to be completely closed. (Do not lock the door unless you see an improvement in shielding efficiency and temperature stability of the crystal frequency.). If you find that in your application leaving the door of the Faraday cage wide open does not result in any external influences on the frequency reading, you may leave them open. Normally, Faraday cage does not need to be grounded with additional wires. You can connect the Faraday cage chassis to the AC ground or water pipe using a thick grounding cable, if necessary. Make this connection only if you see an improvement in shielding or reduction in noise. Avoid creating ground loops! The Nanobalance Instrument (EQCN-900F) is connected to the AC ground through the HP type 3-conductor power cable. With a short banana-to-banana cable, you may connect the chassis of your potentiostat to the chassis of the Nanobalance Instrument EQCN-900F using the CHASSIS banana socket (metal hex nut) on the back panel of the EQCN-900F. You can also use this socket for reference purposes or to connect to other instruments which need to be grounded. The analog ground of the EQCN-900F is provided on the back panel (black banana socket marked GND) for reference purposes. Normally, do not connect anything to this socket. However, you can short it to the AC ground (CHASSIS) or to the analog ground of the potentiostat if necessary. Remove all unnecessary cables from the instrument before doing measurements. (Cables which are not connected on the other end may act as antennas and should also be removed. Note that some measurement instruments, e.g. oscilloscopes, have often the cable guard shorted to the AC ground. Making a connection to such an instrument is equivalent to shorting the analog ground of Nanobalance Instrument to the AC ground.).

Since the oscillating circuit is connected to the electrochemical cell through the working electrode, changes in position of wires connected to the Reference and Counter Electrodes with respect to ground planes may result in some frequency change due to the change in parasitic capacitance. Make sure that all electrodes are firmly attached to the cell top and the connecting wires are short and do not bounce during measurements. The connections between the working quartz crystal and the Remote Probe Unit (blue and white tip banana jacks) should be as short as possible and the inter-wire capacitance should be kept constant during measurements.

23


In the piezogravimetric technique, we do not measure the absolute mass of the working electrode but rather the mass change that occurs during the experiment. At the beginning of the experiment, you set the initial mass to zero (or any other value you wish) using the mass OFFSET potentiometers located on the front panel of the instrument. Due to the high sensitivity of measurements (compare it with a regular balance), it is essential that you maintain all the system parameters (including parasitic capacitances of connecting wires and cables) constant. Only then the frequency change observed during the experiment will correspond to the change in values of parameters of the equivalent circuit of the quartz crystal assembly (especially the inductance change proportional to the change in mass rigidly attached to the working electrode).

With electrochemical cells, a significant frequency change (observed as a drift) may occur even at constant potential due to surface changes, adsorption, poisoning, etc. Use only high purity chemicals. Please keep in mind that the gold substrate may undergo slow dissolution at higher potentials which may lead to the apparent mass decrease (absolute frequency increase). Very often mass changes may result as a consequence of the surface oxide formation. Sudden metal dissolution may result in oversaturation and deposition of salts on the electrode surface. Deposits on the surface may be sometimes difficult to remove and may block the surface and change the electrode activity. If you are not familiar with electrochemistry at solid electrodes, consult general textbooks and monographies (e.g., A. J. Bard and L. R. Faulkner, Electrochemical Methods, J. Wiley and Sons, New York, 1980).

WARNING: Do not attach ground wires to a gas or heating pipe.

4.5. THERMAL SENSITIVITY

As with any electronic equipment, this instrument should be warmed up in order to achieve the greatest accuracy. Under normal circumstances, the frequency difference readout on the front panel of the instrument should be stable to 1-2 Hz after 15 minute warmup and the mass change readout should stabilize in 30 minutes. In order to reduce the heat generation, it is recommended to set the QCI section OFF when precision EQCN measurements are made.

24

5. INSTALLATION

5. INSTALLATION

The operating instructions have been made short and simple but make sure they are followed in this exact order. Bold letters indicate connections and controls on the EQCN-900F system only. For the sake of clarity, the Model EQCN-900F is often referred to in the text as the Nanobalance Instrument or the Instrument. The other two system components are: Model EQCN-900F-2 Faraday Cage and the Model EQCN-900-3 Remote Probe Unit which is factory mounted on the back of the Faraday Cage.

5.1. Initial set-up

(1) Unpacking.Carefully remove all paper and tape used in shipping. Place instrument on a convenient bench. Check the items against the packing list.

(2) The Faraday Cage (EQCN-900F-2) should be placed on the bench on the left side of the Nanobalance Instrument (EQCN-900F) to have the connections as short as possible. The Remote Probe Unit, Model EQCN-900-3, has been mounted on the back of the Faraday Cage in the factory.

(3) This instrument has been set for either 110 or 220 V a.c., 50-60 Hz, power supply. If necessary, you can change this setting by changing the position of the supply voltage selector 110/220 located on the back panel of the instrument. If you have to make the change, make sure the power in the instrument, AC, and in all other devices is off, and nothing is connected to the instrument or the Faraday Cage. With the power cord disconnected from the instrument, set the power supply voltage switch to the appropriate position, 110 or 220 V. Connect the power cord back to the instrument.

(4) Connect the 8-conductor cable with 8-pin audio-type connectors to the sockets marked SPLY on the back of the instrument and to the corresponding socket on the side panel of the Faraday Cage.

(5) Connect the multiconductor cable with standard DB-25 connectors to the sockets marked I/O on the back panel of the instrument and to the corresponding socket on the side panel of the Faraday Cage.

25

5. INSTALLATION

(6) Connect the BNC socket labeled ΔF-IN on the back panel of the Instrument to the corresponding BNC socket on the side panel of the Faraday Cage marked ΔF-OUT using the coaxial cable provided.

(7) Connect the V-OUT BNC socket on the back panel of the Instrument to the input of the recorder or, if you use an ELCHEMA data acquisition system, to the M input BNC cable of the Break-Up Box DAQ-617.

(8) Put the QCI toggle switch to the OFF position.Put the MODE switch to the EQCN position (for Quartz Crystal

Nanobalance measurements).

(9) Put the RANGE selector to 100 μg position (least sensitive).

(10) Put the ATTENUATION switch to '1 (mA/V)'.

(11) Put the mass change POLARITY (+/-) switch to the + (plus) position.

(12) Zero the recorder.

(13) Set the range on the recorder to 10 V.

26

5. INSTALLATION

27

5. INSTALLATION

28

5. INSTALLATION

5.2. Power ON checks

(1) Turn the power switch ON.

(2) Set the MODE switch to EQCN.

(3) Set the output FUNCTION to MASS.

(4) Set the METER mode to V-OUT.

(5) Set the OFFSET toggle switch OFF.

(6) Set the FILTER selector to the first (top) position.

(7) Connect pin tip plugs from the Crystal-Cell assembly (ROTACELL, Model RTC-100) to the white and blue pin tip jacks CRYSTAL, inside the Faraday Cage, in the EQCN section. These jacks are labeled AIR and SLN (SOLUTION), respectively. Insert an EQCN cell with quartz crystal in the ROTACELL (For Crystal-Cell assembly instructions refer to Chapter 5.)

(8) At this point, the frequency meter should give you some frequency difference reading. Typical values are from 500 Hz to 90 kHz. If the reading is 0, the contacts to the working crystal may not be good or crystal cannot oscillate due to a strong damping (thick film deposited on the crystal, broken crystal, etc.).

(9) Note the voltage at the output. The recorder output voltage V-OUT is 10 V per nominal mass range (FS).

(10) Set the OFFSET toggle switch ON. Use the COARSE and FINE OFFSET knobs to set the mass reading on the panel METER to zero. You can now change the MASS RANGE to more sensitive one. Again, use the COARSE and FINE OFFSET knobs to set the MASS reading on the MASS panel meter to zero.

(11) Repeat the operations (10) until the MASS RANGE with desired sensitivity is selected.

(12) In the following testing, observe the rules:- Start experiments with MASS change set to zero (or close to zero).- Before disconnecting Working Crystal change the mass RANGE to 100 μg.

29

5. INSTALLATION

5.3. Connections to a potentiostat and electrochemical cell

The EQCN-900/PS-705 system does not require any external connections between the potentiostat and the balance for EQCN measurements so you can skip procedures (1)-(3). When connecting potentiostats from other vendors, make sure that the shields of cables to WE, CE, and REF electrodes can be safely grounded. The WE electrode should be maintained at the ground potential by the potentiostat. The best performance is achieved with PS-205A/B, PS-305 and PS-605E potentiostats which are specially tuned to work best with EQCN systems. First, make the following onnections:

(1) Connect the working electrode output in potentiostat to the WE BNC input on the side panel of the Faraday Cage.

(2) Connect the reference electrode input in potentiostat to the REF BNC output on the side panel of the Faraday Cage.

(3) Connect the counter (auxiliary) electrode output in potentiostat to the CE BNC input on the side panel of the Faraday Cage.

Connect the electrodes as follows:

(4) First, make sure, that the potentiostat CELL switch is set to OFF (or to a DUMMY CELL) position.

(5) Connect the Counter Electrode to the red pin tip jack CE inside the Faraday Cage.

(6) Connect the Reference Electrode to the yellow pin tip jack REF inside the Faraday Cage.

(7) Make sure that the working crystal is connected to the white and blue pin tip banana jacks marked CRYSTAL, Air and Sln, respectively, inside the Faraday Cage, in the EQCN section. (For Crystal-Cell assembly instructions refer to Chapter 5.)

(8) You are now ready to start your experiment. Refer to the next section to learn the details of the experimental procedure illustrated with an example of the deposition and stripping of copper.

30

5. INSTALLATION

5.4. Testing experiment with real cell ON

(1) You are now ready to use the instrument for measurement purposes. If you want to perform a simple checking experiment, you can use, for example, a 5 mM copper(II) solution in 0.1 M H2SO4 . Program your waveform generator for sweep from 500 mV vs. SCE to 0 mV.

(2) Check if the Reference Electrode is connected and placed in the solution.

(3) Check if the Counter Electrode is connected and placed in the solution.

(4) Set the current range on your potentiostat to 1 mA FS (full scale).

(5) Turn the CELL switch on your potentiostat to the ON (or: EXTERNAL CELL) position.

(6) Initiate the potential scan. Using the OFFSET knobs, appropriately position the mass response curve on the recorder chart, or monitor plot.

(7) Change carefully the cathodic potential limit to more negative value until copper deposition just begins to take place. On the voltammogram, you should be able to observe an increase in cathodic current due to copper deposition, and an increase of the anodic peak due to the copper stripping. On the mass-potential curve which can be recorded simultaneously with the current-potential curve, you should observe a mass histeresis with mass increase in the potential region where copper is being deposited, and a mass decrease which is fastest in the region of the stripping current peak. If mass changes in the opposite direction, change the POLARITY switch (+/-) setting. (When the working crystal frequency is lower than the reference crystal frequency, the mass increase is manifested by the increase in the measured frequency difference. When the working crystal frequency is higher than the reference crystal frequency, the mass increase is manifested by the decrease in the measured frequency difference.)

Do not deposit too much copper. During the anodic stripping process, very often a high concentration of the dissolved metal builds up in the vicinity of the electrode surface, and it may result in the formation of metal oxides on the electrode surface (the oxides may be sometimes difficult to remove).

Depending on your experiment and the range of your frequency measurement you may wish to increase the sensitivity of measurements by changing the RANGE selector or by increasing the sensitivity of the recorder, e.g., to 500 mV. (Be careful with whatever changes you make in instrument settings and connections because the instrument is capable of outputing 15V at the RECORDER V-OUT). If you want to change the RANGE selector to more sensitive range, first offset the mass reading to zero (or close to zero) with COARSE and FINE offset potentiometers. The

31

5. INSTALLATION

offset potentiometers will allow you to do measurements at high sensitivity on large signals.

5.5. Quartz Crystal Immittance Measurements

To follow the changes in quartz crystal motional characteristics, the quartz crystal under test is typically subjected to oscillations controlled by an independent oscillator (eg. a function generator) able to scan the frequency around the resonance frequency of the crystal. To avoid interferences with the high speed potentiostat circuitry and high precision EQCN circuitry, in the EQCN-900F an external function generator is used for the quartz crystal excitation purpose (eg. an ELCHEMA Model EQCN-906). The input of the frequency scanning generator F-SCAN IN is optically isolated from the EQCN-900F circuits to reduce noise caused by digital part of the external generator.

An example of the QCI measurement procedures is presented below.

(1) Turn ON the EQCN-900F system.

(2) Set the external generator for the following output waveform and scanning characteristics:

Function: square waveAmplitude: 5 Vp-p

Offset: 0 VStart Frequency: 9.940 MHzStop Frequency: 10.060 MHzSweep Time: 60 s

This should supply a square wave of 0 to +5 V, with frequency scanned between 9.940 MHz to 10.060 MHz which should cover the frequency range of our laboratory crystals. The frequency scan should be completed in τscan = 60 s.

WARNING: Check the output waveform of the external generator using an oscilloscope to make sure that it does not exceed the input voltage limit of the EQCN-900F, which is 5 V. (Although the EQCN-900F is protected, avoid supplying any signals to the EQCN-900F when the power to the instrument is OFF).

(3) Connect the BNC socket marked F-SCAN IN on the side panel of the Faraday Cage to the output of the frequency scanning generator, e.g. Model EQCN-906.

(4) Insert the QC Holder, Model CB-AC-1, to the white and blue pin tip banana jacks marked CRYSTAL, AIR and SLN, respectively, inside the Faraday Cage, in the QCI section. If you do not have the QC Holder, use two short

32

5. INSTALLATION

cables with pin-tip bananas on one side and aligator clips on the other side to connect a test quartz crystal.

(6) With the right hand, press both aligators of the QC Holder open and insert a quartz crystal to be tested, such that each contact pin of the crystal makes an electrical contact with the metal body of one of the aligators. Release the aligator clamps. (Note that the plastic insulator on the outside of the aligator clips does not make an electric contact.).

(7) Connect the VQC output BNC socket on the back panel of the Nanobalance Instrument to the corresponding socket on the Data Logger back panel..

(8) Connect the IQC output BNC socket on the back panel of the Nanobalance Instrument to the corresponding socket on the Data Logger back panel..

(9) Connect the (Phase Detector) output BNC socket on the back panel of the Nanobalance Instrument to the corresponding socket on the Data Logger back panel..

(10) Turn the QCI toggle switch ON. Wait 15 minutes to warm up the QCI section an the temperatures to stabilize.

Set the MODE switch to the QCI position.

(11) Set the ATTENUATION switch to the position 10 (10 mA/V).

(11) Put the mass change POLARITY (+/-) switch to the + (plus) position.

(12) In QCI program in Data Logger, set the variables on the VARIABLES page of the Tabbed Notebook as follows:x: f frequency MHzy: |Y| Y modulus mSz fi phase shift deg

(13) In QCI program, set the plot scale on the SCALE page of the Tabbed Notebook as follows:

variable units/V min max f 1 -105 105 |Y| 1 -500 500 fi 45 -500 500

(14) Turn the external Waveform Generator ON.

(15) Initiate the frequency sweep by clicking on the PRE-SCAN button on FSCAN page of the Tabbed Notebook in QCI program in Data Logger, followed by clicking on the RUN button located on the Run Panel which appears on the right-side of the screen.

(16) Observe the shape of the curve recorded. There should be a peak close to the resonance frequency of the quartz crystal. After the scan is finished , click on the ANALYZE button on the cool bar and check the characteristics of the admittance curve recorded. Then try the SIMULATE and/or EVALUATE

33

5. INSTALLATION

buttons for further data processing. Consult the QCI manual for standard procedures and sample graphs obtained for QC in air and in solution.

(17) Set now a narrower frequency scan, but still covering both the admittance maximum and minimum. This usually results in an improvement in the evaluation of the equivalent circuit elements. Please note that the evaluation is basically not a strict fitting, so if you want to scan only over a small portion of the immittance spectrum, use values of passive elements estimated in a wider scan. You can still do simulation by entering values of these parameters.

(18) To perform measurements with EQCN cells, remove the QC fixture and connect the white and blue wires from the ROTACELL assembly to the white and blue pin tip banana jacks in the QCI section inside the Faraday Cage. (For Crystal-Cell assembly instructions refer to Chapter 5.). Follow the procedures (10)-(17) above, with exception of the initial IQC Attenuation, which should be set at 0.5 mV/V.

(18) Shut-off procedure:(i) - Set the QCI toggle switch to OFF.

Set the MODE toggle switch to EQCN.(ii) - Set the CELL off, CONTROL off, and then also PROGRAM off on

your potentiostat.(iii) - Turn OFF the EQCN-900F, potentiostat, generator, recorder,

computer, and other instruments, if any.

5.6. Other utilities (Optional)

(1) The frequency difference may be viewed and measured externally by connecting a measuring device to the ΔF-OUT BNC output located on the side panel of the Faraday Cage. This output provides a sinusoidal wave, 0.4 Vp-p. (When connected to the ΔF-IN input on the back panel of the Nanobalance Instrument, frequency of this signal is displayed on the ΔF FREQUENCY panel meter).

(2) The absolute frequency of the working oscillator WO and the reference oscillator RO may be viewed and measured externally by connecting a measuring device to the F-OUT BNC output located on the side panel of the Remote Probe Unit attached to the Faraday Cage. This output provides a high frequency wave (ca. 10 MHz), approximately 0 to 5 V. Use only short concentric cables (2-3 feet) to connect the F-OUT BNC socket to the measuring device (an oscilloscope or frequency meter). The WO and RO are selected with the toggle switch F-OUT located above the F-OUT BNC socket.

34

5. INSTALLATION

(3) This instrument may by used as a Frequency Meter and a Frequency-to-Voltage Converter. To do this, connect the frequency source to the BNC input socket marked ΔF-IN on the back panel of the Nanobalance Instrument. The voltage on this input must not exceed 5 Vp-p. Set the OUTPUT FUNCTION toggle switch on the front panel to the FREQUENCY position. Frequencies up to 100 kHz can be measured and converted to an analog signal with a maximum sensitivity of 100 mV/Hz (on 100 ng range). OFFSET can be used to monitor small frequency changes around larger center frequency.

(4) The FILTER selector switch controls a filter which damps the noise of the output voltage at the recorder V-OUT BNC socket on the back panel of the Instrument. Use a setting which works best for the particular experiment you are doing. Make sure that the damping acts only on the high frequency noise and not on the (slower) signal. The obtained curve should be more smooth (less noisy) but not more sluggish (signal should be intact). The time constants of the FILTER are specially selected for typical scan rates used in cyclic voltammetry and microelectrogravimetry experiments. Usually, the first or second setting, from the top (or left), is appropriate. The filter time constants increase, from top to bottom (or from left to right), in the following order:

_____________________________________________________FILTER TIME INDICATORPOSITION CONSTANT NUMBER

ms_____________________________________________________

0 none none (all OFF)1 10 12 40 23 80 34 200 45 1000 5_____________________________________________________

The damping FILTER can be used for both the MASS and FREQUENCY output FUNCTION (for the FREQUENCY output function, the output voltage corresponds to the frequency shift, rather than the mass change).

The EQCN-900F has been designed for the highest speed of mass change measurements in mind. With the FILTER OFF, very fast mass transients can be recorded with the noise floor on the order of single nanograms. Although the mass change rate may be limited by the solution transport rate of mass-changing species, a 30 s per point recording is the fastest available.

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6. CRYSTAL-CELL ASSEMBLY


6.1. Mounting Quartz Crystals

(1) Remove the rubber band and the metal cover can of the quartz crystal.

(2) Carefully bend the contact spring wires close to the quartz crystal, such, that after sealing, the gold working electrode to be immersed in the solution will contact the blue wire and blue pin tip jack marked Liquid or Sln (Solution), inside the Faraday Cage.

(3) Glue the crystal to the side opening in the cell.

6.2. Assembling Piezocells in ROTACELL Holder

(1) Once the glue is dry, place the cell into the ROTACELL holder and adjust the height of the bottom support if necessary.

(2) Press the clip lever open and lock it in this position with the clip support by turning clockwise the black anodized aluminum knob in the bottom plate of the ROTACELL.

(3) Rotate the cell top plate (with the reference and counter electrodes) clockwise, out of the Faraday Cage, and place the cell underneath. Hold the cell and rotate it together with the cell top back to the initial position (inside the Faraday Cage). The quartz crystal sealed to the cell should be directed toward you so that the contact pins extending from the crystal will not be damaged by the clamp fixture. After the cell top, with the cell, is rotated back into the Faraday Cage and the cell is fully supported by the bottom plate of the ROTACELL, carefully turn the cell clockwise until the crystal pins slide onto the disk shaped contacting metal pads which are hot-pressed into the clamp base block.

(3) While pressing firmly the clip lever, release the clip support by turning the black anodized aluminum knob in the bottom plate counter-clockwise. Then,

36


by slowly releasing the clip lever, lower the clip jaw until it touches the crystal pins and secures their contact to the metal pads.

NOTE: If the crystal pins do not move unobstructed to the contact plates of the clip, remove the cell and gently pull the crystal pins to bend the spring wires. Once the pins are positioned flat on the contact plates, release the clip lever. If the crystal pins are not on the level of the contact metal pads, adjust the height of the clip base block using the spring loaded screws beneath the base plate.

(4) Check if the cell is tightly positioned in the holder. If it is loose, press the clip to free crystal pins, and remove the cell from the holder. Adjust the bottom support level and start from (2), again.

6.3. Disassembling Piezocells from ROTACELL Holder

(1) To remove the cell from the ROTACELL holder, press the clip lever open and lock it in this position with the clip support by turning clockwise the black anodized aluminum knob in the bottom plate of the ROTACELL.

(2) Very carefully rotate the cell counter-clockwise to free the crystal pins from the clip.

(3) Now, holding the cell and the top plate with the right hand, rotate them clockwise, out of the Faraday Cage, while keeping the bottom plate from moving with the left hand. Remove the cell by moving it downward. Clean the reference electrode and counter electrode.

6.4. Final checks

(1) Check the assembly in order to avoid a short circuit across the contact plates in the clip.

(2) Make sure there is no significant strain on the crystal pins.

(3) Make sure there is no solution spills on the air-side of the quartz crystal. Any mass change on the air-side of the quartz crystal will also influence the frequency of oscillation.

37

7. ELECTRIC CIRCUITS


38


WO and ROBUFFERS

FIGURE 6. Block diagram of Model EQCN-900F, the nanobalance converter unit.

SCALINGOP. AMPS.

TIMEBASE

COUNTERLOGIC

FREQUENCYMETER

f/VCONVERTER

ACTIVEFILTER

VOLTAGEOFFSET

OUTPUTFILTERS

DIGITALPANEL METER

V-out(M-

f-in

39


ROREFERENCEOSCILLATOR

OPTICALISOLATION

FREQUENCYDIFFERENCE

fBUFFER

WO and ROBUFFERS

Reference QC

Working QC inelectrochemical

cell

WOWORKING

OSCILLATOR

FIGURE 7. Block diagram of electronic circuits of the nanobalance unit mounted in the Remote Probe Unit in Faraday Cage.

OPTICALISOLATION

Reference Frequency Selector

Ext. Freq. Ref.Input

f-OUT

f-OUT

40


41

8. SERVICING NOTES

8. SERVICING NOTES

In case of malfunction of the EQCN-900F instrument, the unit may be returned to the factory for service. It should be returned postpaid. Since the equipment is guaranteed for one year, no charges for repair will be made for time and materials. The guarantee does not cover misuse of the Model EQCN-900F or damage due to improper handling or service.

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9. WARRANTY

WARRANTY

All our products are warranted against defects in material and workmanship for one year from the date of shipment. Our obligation is limited to repairing or replacing products which prove to be defective during the warranty period. We are not liable for direct, indirect, special, incidental, consequential, or punitive damages of any kind from any cause arising out of the sale, installation, service, or use of our instrumentation.

All products manufactured by ELCHEMA Company are thoroughly tested and inspected before shipment. If ELCHEMA receives notice from the Buyer of any defects during the warranty period, ELCHEMA shall, at its option, either repair or replace hardware products which prove to be defective.

Limitation of WarrantyA. The Warranty shall not apply to defects resulting from:

1. Improper or inadequate maintenance by Buyer;2. Unauthorized modification or misuse;3. Operation in corrosive environment (including vapors, solids, and aggressive solvents);4. Operation outside the environmental specification of the product;5. Improper site preparation and maintenance.

B. In the case of instruments not manufactured by ELCHEMA, the warranty of the original manufacturer applies.

C. Expendable items, including but not limited to: glass items, reference electrodes, valves, seals, solutions, fuses, light sources, O-rings, gaskets, and filters are excluded from warranty.

THE WARRANTY SET FORTH IS EXCLUSIVE AND NO OTHER WARRANTY, WHETHER WRITTEN OR ORAL, IS EXPRESSED OR IMPLIED. ELCHEMA SPECIFICALLY DISCLAIMS THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.

For assistance of any kind, including help with instruments under warranty, contact you ELCHEMA field office of instructions. Give full details of the difficulty and include the instrument model and serial numbers. Service date and shipping instructions will be promptly sent to you. There will be no charges for repairs of instruments under warranty, except transportation charges. Estimates of charges for non-warranty or other service work will always be supplied, if requested, before work begins.

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9. WARRANTY

CLAIM FOR DAMAGE IN SHIPMENT

Your instrument should be inspected and tested as soon as it is received. The instrument is insured for safe delivery. If the instrument is damaged in any way or fails to operate properly, file a claim with the carrier or, if insured separately, with the insurance company.

SHIPPING THE INSTRUMENT FOR WARRANTY REPAIR

On receipt of shipping instructions, forward the instrument prepaid to the destination indicated. You may use the original shipping carton or any strong container. Wrap the instrument in heavy paper or a plastic bag and surround it with three or four inches of shock-absorbing material to cushion it firmly and prevent movement inside the container.

GENERAL

Your ELCHEMA field office is ready to assist you in any situation, and you are always welcome to get directly in touch with the ELCHEMA Service Department:

ELCHEMACustomer SupportP.O. Box 5067Potsdam, NY 13676Tel.: (315) 268-1605FAX: (315) 268-1709

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