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

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1. INTRODUCTION

The Model EQCN-900F Electrochemical Quartz Crystal Nanobalance is ameasurement system for monitoring extremely small variation in the mass of a metalworking electrode. The system allows one also to record the quartz crystalimmittance (QCI) characteristics using an external frequency sweep generator. Theamplitude of the a.c. current flowing through the crystal and the a.c. voltage accrossthe crystal are provided for QCI measurements. The EQCN-900F System consists ofa 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. Theworking electrode is in the form of a thin film, and is placed on one side of a quartzsingle 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 thechange of the quartz crystal oscillation frequency. The frequency of the workingquartz crystal is compared to the frequency of the standard reference quartz crystal.The frequency measurements are differential, i.e. the frequency of the referencecrystal is subtracted from the frequency of the working crystal. The obtainedfrequency difference is then measured by a precision frequency counter anddisplayed on the front panel. The frequency difference is converted to a voltagesignal, calibrated in Sauerbrey mass units (referred to as the effective mass) andoutput to an analog recorder, or analog-to-digital converter.

Typical processes leading to the frequency change which corresponds to theeffective 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 filmsintercalationcoadsorption and competitive adsorptionmoisture accumulation (from gaseous phase)etc.

1. INTRODUCTION

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

The resolution of the EQCN-900F is 0.1 Hz which correspondsapproximately to 0.1 ng of the effective mass change. The short-term stability ismostly dependent on the state of the working electrode surface and purity of thesolution. Usually, it is better than 5 Hz. The exceptional linearity of massmeasurements extends up to 100 _g. The use of AT-cut quartz crystals reducestemperature coefficient to the minimum. Under normal circumstances, the effect oftemperature can be neglected in the range near the room temperature. If a very highsensitivity or wide temperature range are required, it is recommended to use athermostatted cell and Model EQCN-900-3B Remote Probe Unit with thermostattedreference oscillator, or Model EQCN-900-4 Remote Probe Unit with externalreference quartz crystal.

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

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

2. SPECIFICATIONS

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2. SPECIFICATIONS

Measurement Functions

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

Oscillators

Working 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 Ranges

Frequency 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 _g,-10.00 to +10.00 _g,-1.000 to +1.000 _g,-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(_m > 0, mass increase)

Overload Indicator ..................................................... ca. 3 % over nominal range

Resolution

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

2. SPECIFICATIONS

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

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

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

Sensitivity

Quartz 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/V

Quartz Crystal a.c. Voltage Amplitude: ........................ 200 mV (constant)Phase Detector Output (_, PD-OUT): ........................... 45 deg/V

(i.e. -90 deg ⇔ -2 V, +90 deg ⇔ +2 V)

Calibration:IQC, _: ............................................................. 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(_g or kHz) ∀100.0 0.100 V/_g 0.100 V/kHz ∀10.00 1.000 V/_g 1.000 V/kHz ∀1.000 10.00 V/_g 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 _g or 90 kHz (approx.)fine: ................................................... 0 to 900 ng or 900 Hz (approx.)

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

Recorder Outputs

Analog 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 (φ, PD-OUT): ................................. -3 to +3 V

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

2. SPECIFICATIONS

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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, _: ........................................................... softwareVQC, _m, _f: .................................................. 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 ControllerModel 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

3. CONTROLS

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3. CONTROLS

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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 theinside panel of the Faraday Cage is shown in Figure 4.

Read this Chapter carefully since it provides you with a full and systematicdescription of the functionality and limitations of all features and facilities availablein the instrument. For exemplary schematics of connections and experimentalmeasurement 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 QCImeasurements, set the QCI switch ON and allow 15 minutes to warm up and stabilizethe 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 toachieve 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 (_F) panelmeter corresponds to the difference between the frequency of the EQCN workingoscillator and the reference oscillator (either the one sealed inside the RemoteProbe Unit or an external reference oscillator).

QCI - for Quartz Crystal Immittance measurements

3. CONTROLS

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ELCHEMAF

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

3. CONTROLS

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

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

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

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

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

5. OFFSET Toggle switch to turn the offset for M A S S or FREQUENCY in EQCNmeasurements ON or OFF.

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

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

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 outputmode is selected. The V_m signal can be used to monitor apparent mass changesduring 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 _fac (an a.c. signal) tothe analog dc voltage V_f proportional to the frequency of the _fac signal. TheV_f voltage is displayed on the Mass/Frequency METER in V-OUT mode and isalso available at the V-OUT BNC socket on the back panel of the instrument

3. CONTROLS

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when the FREQUENCY output mode is selected. The V_f signal is scaled tohave a sensitivity of 10 V per nominal frequency shift RANGE and can be usedto monitor the frequency shift related to apparent mass changes and/or changes inviscoelastic properties of a solution and an electrode film during experimentswhen the EQCN mode and FREQUENCY output mode are used. The outputvoltage 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 therange selection, from ∀100 to ∀0.1 _g, or ∀100 to ∀0.1 kHz FS, depending on theoutput FUNCTION switch setting, MASS or FREQUENCY, respectively. Therange selected is indicated by a lighting diode. For each range, the extended linearityfrom -110% to +110% of the range value can be utilized.

Adjustable Potentiometers

8-9. OFFSETTwo multiturn precision low-noise potentiometers marked COARSE and FINE forprecision offset of the amplified mass signals. An exact zero offset can be obtainedby setting the OFFSET toggle switch OFF. When the OFFSET toggle switch isON, the zero offset can be obtained by turning both potentiometers clockwise until aresistance is felt (with the POLARITY switch in '+' position). Set a zero mass on the100 _g first, then increase the sensitivity by switching to the 10 _g range and re-adjust the FINE offset knob position. Apply the same procedure on more sensitivemass ranges, if necessary.

In the EQCN measurements, usually the offset is not set to zero (that is: _m= 0 on the Mass METER, with the crystal disconnected) but rather the offset isadjusted (to whatever value) to have a zero mass reading on the Mass METER withthe crystal connected to the internal EQCN oscillator. This allows the experimenterto 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 wedo not measure the absolute mass of the electrode but rather the mass change duringthe experiment. It is therefore convenient to start the experiment from a zero massreading.

Panel Meters

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

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

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

Usually, the mass reading is adjusted (using OFFSET knobs) to zero justbefore 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 theelectrode but rather the mass change during the experiment. Similar concerns thefrequency shift See also how the POLARITY switch affects the mass readings.

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

Diode Indicators

12. OVERLOADRed LED activated when the measured mass change (frequency shift) exceeds theactual 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, thefilter is disconnected. The time constant of the filter increases from left to right (10ms 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 outputvoltage at the recorder V-OUT BNC socket on the back panel of the Instrument. Usea setting which works best for the particular experiment you are doing. Make surethat 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

3. CONTROLS

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constants increase, from top to bottom, in the following order: 10, 40, 80, 200, 1000ms. 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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3.2. BACK PANEL1. _F-IN BNC socket for connection to the socket marked _F-OUT on the side panel of the

Faraday Cage. This connection is necessary in the EQCN mode. Optionally, it mayalso be utilized to perform a precision F-to-V conversion, e.g. to convert frequency ofan external source, up to 100 kHz, to a DC voltage proportional to the inputfrequency. The DC voltage is output to V-OUT and is also displayed on the METERDPM. The input signal should have an amplitude 0.1 to 2.5 V (i.e. 0.2-5.0 Vp-p) andthe 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 workingquartz crystal (for the FUNCTION switch in the MASS position);(b) frequency shift corresponding to the mass change or any change in visoelastic orother properties of the solution or films on the quartz crystal (for the FUNCTIONswitch in the FREQUENCY position).

3. IQC BNC output socket providing a rough analog voltage signal representing the currentflowing through the quartz crystal under test in the QCI measurements. This outputsignal is offset and calibrated by the Data Logger under QCI 2.0 software andconverted 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 thea.c. voltage across the quartz crystal under test in QCI measurements. This signal isconstant (100 to 300 mV, typically: 200 mV).

5. PD, φ BNC output socket providing output from digital Phase Detector. The analog voltagesignal is from -2 to +2 V for phase shift of +90o to -90o (±3.5 V max), i.e. the sign isreversed. After offset and calibration by the Data Logger, the φ signal has thesensitivity of 45 deg/V and zero offset (-2 V corresponding to -90 deg and +2 Vcorresponding to +90 deg). At frequencies lower than the resonance frequency, thephase shift is positive (the current is leading the voltage). At the resonance, the phaseshift passes through zero and becomes negative (the current is lagging the voltage).At the anti-resonance, the phase shift again passes through zero and becomespositive. The phase detector output may have a higher uncertainty when the QCcurrent 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 beconnected to the corresponding male DB-25 connector on the side panel of theFaraday Cage.

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

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3. CONTROLS

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

9. CHASSISBanana socket shorted to the instrument chassis. The instrument chassis is connectedinternally to the power line ground wire (a.c. ground). You can use this socket forreference 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. Ifthe 110/220 V switch is not set properly for your power supply voltage, remove thepower cord from the instrument and change the position of the 110/220 V selector tothe 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 USAand Japan, and 220 V, elsewhere. Check the position of this switch before youconnect power to the instrument.

WARNING: Make sure the power in the instrument is OFF and power cord removedfrom 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 isdisconnected from the instrument before you replace the fuse.

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

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

1. RE BNC socket for connection to the Reference Electrode input in your potentiostat. Makesure 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. Makesure 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. Makesure 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 shortedto GND).

4. F-SCAN INBNC input socket for connection to a Frequency Scanning Generator, e.g. ELCHEMAFG-906S providing a TTL/CMOS compatible squarewave with frequency scanned in therange 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 levelsare 0 and +5 V. The generator must be able to provide 50 mA current without anychange in the voltage amplitude. The rise time and fall time should be on the order of 5ns or shorter. The generator should have an exceptional frequency stability (DDS withoven stabilized oscillator is a must).

5. EXT.REF. INBNC input socket for connection to a stable frequency source, e.g. ELCHEMA FG-806providing 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 externalreference frequency instead of the internal frequency reference. The external frequencystandard is to be utilized in the EQCN measurement mode. The TTL/CMOScompatibility 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 voltageamplitude. The rise time and fall time should be on the order of 5 ns or shorter. Thegenerator should have exceptionally good frequency stability (for FG-806 it is 0.001 ppm,or 10-7 %).

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

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RE

CE

WE

F-SCANIN

IN

ΔF-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

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

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7. F-OUT BNC output socket providing a high frequency signal fWO, fRO, or fEXT.REF selected by theF-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 measuredusing an external high frequency counter.

8. FLOAT/GND toggleToggle switch to select a floating or grounded EQCN working oscillator. When EQCN isused with potentiostat, the working electrode should be maintained on the groundpotential 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. TheFaraday 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 ExternalReference Oscillator (EXT) as the frequency reference for _f measurements.

10. F-OUT toggleThree-position toggle switch to select frequency for output at the BNC output socketmarked 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 tothe corresponding female DB-25 connector on the back panel of the NanobalanceInstrument.

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

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3.4. Faraday Cage: Internal Panel

1. REF REFERENCE ELECTRODE yellow pin tip banana jack for connection to thereference electrode (e.g., saturated calomel electrode, SCE, or a double-junctionsilver/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 counterelectrode (auxiliary electrode) in the electrochemical cell for experiments involving apotentiostat. Use a short wire for the connection.

3. AIR (EQCN)White pin tip banana socket for connection to the electrode exposed to air in theEQCN cell assembly. Use this socket for EQCN measurements only. The MODEswitch 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 thesolution. This is a connection to your working electrode deposited on the quartzcrystal. Use this socket for EQCN measurements only. The MODE switch on thefront 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 toair. Use this socket for QCI measurements only. The MODE switch on the frontpanel of the Nanobalance Instrument must be set to QCI . This socket is notconnected to the AIR (EQCN) white jack (3).

6. SLN (QCI)Blue pin tip banana socket for connection to the quartz crystal electrode immersed inthe solution. This is a connection to your working electrode (the sensor) depositedon the quartz crystal. Use this socket for QCI measurements only. The MODEswitch on the front panel of the Nanobalance Instrument must be set to QCI. Thissocket is not connected to the working electrode input of the potentiostat. It is alsonot 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) inputon the side panel of the Faraday Cage (Remote Probe Unit) and have no galvanicconnection to it.

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

AIR

AIR

SOLN

SOLN

EQCN

QCI

3

REF

CE

1

2

4

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4. OPERATING INSTRUCTIONS

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4. OPERATING INSTRUCTIONS

4.1. INSPECTION

After the instrument is unpacked, the instrument should be carefully inspected fordamage received in transit. If any shipping damage is found, follow the procedure outlined inthe "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 theguidelines for maximum voltage at the inputs. There should be no signal applied to the inputswhen the instrument is turned off. The outputs should not be loaded. They can only beconnected to high input impedance devices such as plotters or oscilloscopes.

Use minimal force when putting on, or taking off, the BNC connections, otherwisethey might become loose. Push the BNC forward when making a connection or adisconnection 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. Ourcomponents are marked with seals. DO NOT try to open and fix anything yourself, otherwiseyour warranty agreement will be nullified.

4. OPERATING INSTRUCTIONS

23

4.3. FARADAY CAGE

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

4.4. GROUNDING AND INTERFERENCES

It is very important to properly ground the Nanobalance system. The circuitryoperates at a high frequency of 10 MHz and is very susceptible to electromagnetic radiationand interference present in the surroundings. Since the working oscillator can not beenclosed 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 lockthe door unless you see an improvement in shielding efficiency and temperature stability ofthe crystal frequency.). If you find that in your application leaving the door of the Faradaycage wide open does not result in any external influences on the frequency reading, you mayleave them open. Normally, Faraday cage does not need to be grounded with additionalwires. You can connect the Faraday cage chassis to the AC ground or water pipe using athick grounding cable, if necessary. Make this connection only if you see an improvement inshielding 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 thechassis 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 forreference purposes or to connect to other instruments which need to be grounded. The analogground 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 canshort 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. (Cableswhich 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 guardshorted to the AC ground. Making a connection to such an instrument is equivalent toshorting the analog ground of Nanobalance Instrument to the AC ground.).

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

4. OPERATING INSTRUCTIONS

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In the piezogravimetric technique, we do not measure the absolute mass of theworking electrode but rather the mass change that occurs during the experiment. At thebeginning 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 tothe high sensitivity of measurements (compare it with a regular balance), it is essential thatyou maintain all the system parameters (including parasitic capacitances of connecting wiresand cables) constant. Only then the frequency change observed during the experiment willcorrespond to the change in values of parameters of the equivalent circuit of the quartz crystalassembly (especially the inductance change proportional to the change in mass rigidlyattached to the working electrode).

With electrochemical cells, a significant frequency change (observed as a drift) mayoccur even at constant potential due to surface changes, adsorption, poisoning, etc. Use onlyhigh purity chemicals. Please keep in mind that the gold substrate may undergo slowdissolution at higher potentials which may lead to the apparent mass decrease (absolutefrequency increase). Very often mass changes may result as a consequence of the surfaceoxide formation. Sudden metal dissolution may result in oversaturation and deposition ofsalts on the electrode surface. Deposits on the surface may be sometimes difficult to removeand may block the surface and change the electrode activity. If you are not familiar withelectrochemistry 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 toachieve the greatest accuracy. Under normal circumstances, the frequency difference readouton the front panel of the instrument should be stable to 1-2 Hz after 15 minute warmup andthe mass change readout should stabilize in 30 minutes. In order to reduce the heatgeneration, it is recommended to set the QCI section OFF when precision EQCNmeasurements are made.

5. INSTALLATION

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5. INSTALLATION

The operating instructions have been made short and simple but make sure they arefollowed 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 thetext 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 whichis 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 aconvenient 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 ofthe Nanobalance Instrument (EQCN-900F) to have the connections as short aspossible. The Remote Probe Unit, Model EQCN-900-3, has been mounted on theback 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. Ifnecessary, you can change this setting by changing the position of the supply voltageselector 110/220 located on the back panel of the instrument. If you have to make thechange, 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 corddisconnected from the instrument, set the power supply voltage switch to theappropriate 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 socketsmarked SPLY on the back of the instrument and to the corresponding socket on theside panel of the Faraday Cage.

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

5. INSTALLATION

26

(6) Connect the BNC socket labeled _F-IN on the back panel of the Instrument to thecorresponding BNC socket on the side panel of the Faraday Cage marked _F-OUTusing the coaxial cable provided.

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

(8) Put the QCI toggle switch to the OFF position.Put the M O D E switch to the E Q C N position (for Quartz Crystal

Nanobalance measurements).

(9) Put the RANGE selector to 100 _g 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.

5. INSTALLATION

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5. INSTALLATION

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5. INSTALLATION

29

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 theEQCN section. These jacks are labeled AIR and SLN (SOLUTION), respectively.Insert an EQCN cell with quartz crystal in the ROTACELL (For Crystal-Cellassembly instructions refer to Chapter 5.)

(8) At this point, the frequency meter should give you some frequency differencereading. Typical values are from 500 Hz to 90 kHz. If the reading is 0, the contactsto the working crystal may not be good or crystal cannot oscillate due to a strongdamping (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 pernominal mass range (FS).

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

(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 _g.

5. INSTALLATION

30

5.3. Connections to a potentiostat and electrochemical cell

The EQCN-900/PS-705 system does not require any external connections betweenthe 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 toWE, CE, and REF electrodes can be safely grounded. The WE electrode should bemaintained at the ground potential by the potentiostat. The best performance is achieved withPS-205A/B, PS-305 and PS-605E potentiostats which are specially tuned to work best withEQCN systems. First, make the following onnections:

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

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

(3) Connect the counter (auxiliary) electrode output in potentiostat to the CEBNC 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 aDUMMY CELL) position.

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

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

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

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

5. INSTALLATION

31

5.4. Testing experiment with real cell ON

(1) You are now ready to use the instrument for measurement purposes. If youwant to perform a simple checking experiment, you can use, for example, a 5mM copper(II) solution in 0.1 M H2SO4 . Program your waveform generatorfor 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: EXTERNALCELL) position.

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

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

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

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

5. INSTALLATION

32

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

5.5. Quartz Crystal Immittance Measurements

To follow the changes in quartz crystal motional characteristics, the quartz crystalunder test is typically subjected to oscillations controlled by an independent oscillator (eg. afunction 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 EQCNcircuitry, in the EQCN-900F an external function generator is used for the quartz crystalexcitation purpose (eg. an ELCHEMA Model EQCN-906). The input of the frequencyscanning generator F-SCAN IN is optically isolated from the EQCN-900F circuits to reducenoise 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 scanningcharacteristics:

Function: square waveAmplitude: 5 Vp-pOffset: 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 scannedbetween 9.940 MHz to 10.060 MHz which should cover the frequency rangeof our laboratory crystals. The frequency scan should be completed in _scan =60 s.

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

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

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

5. INSTALLATION

33

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

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

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

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

(9) Connect the φ (Phase Detector) output BNC socket on the back panel of theNanobalance Instrument to the corresponding socket on the Data Loggerback panel..

(10) Turn the QCI toggle switch ON. Wait 15 minutes to warm up the QCIsection 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 pageof 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 TabbedNotebook 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 onFSCAN page of the Tabbed Notebook in QCI program in Data Logger,followed by clicking on the RUN button located on the Run Panel whichappears on the right-side of the screen.

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

5. INSTALLATION

34

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

(17) Set now a narrower frequency scan, but still covering both the admittancemaximum and minimum. This usually results in an improvement in theevaluation of the equivalent circuit elements. Please note that the evaluationis basically not a strict fitting, so if you want to scan only over a smallportion of the immittance spectrum, use values of passive elements estimatedin a wider scan. You can still do simulation by entering values of theseparameters.

(18) To perform measurements with EQCN cells, remove the QC fixture andconnect the white and blue wires from the ROTACELL assembly to thewhite and blue pin tip banana jacks in the QCI section inside the FaradayCage. (For Crystal-Cell assembly instructions refer to Chapter 5.). Followthe procedures (10)-(17) above, with exception of the initial IQCAttenuation, 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 byconnecting a measuring device to the _F-OUT BNC output located on theside panel of the Faraday Cage. This output provides a sinusoidal wave, 0.4Vp-p. (When connected to the _F-IN input on the back panel of theNanobalance Instrument, frequency of this signal is displayed on the _FFREQUENCY panel meter).

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

5. INSTALLATION

35

(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 BNCinput socket marked _F-IN on the back panel of the NanobalanceInstrument. The voltage on this input must not exceed 5 Vp-p. Set theOUTPUT FUNCTION toggle switch on the front panel to theFREQUENCY position. Frequencies up to 100 kHz can be measured andconverted to an analog signal with a maximum sensitivity of 100 mV/Hz (on100 ng range). OFFSET can be used to monitor small frequency changesaround larger center frequency.

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

_____________________________________________________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 andFREQUENCY output FUNCTION (for the FREQUENCY output function,the output voltage corresponds to the frequency shift, rather than the masschange).

The EQCN-900F has been designed for the highest speed of masschange measurements in mind. With the FILTER OFF, very fast masstransients can be recorded with the noise floor on the order of singlenanograms. Although the mass change rate may be limited by the solutiontransport rate of mass-changing species, a 30 µs per point recording is thefastest available.

6. CRYSTAL-CELL ASSEMBLY

36

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, thatafter sealing, the gold working electrode to be immersed in the solution willcontact 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 adjustthe height of the bottom support if necessary.

(2) Press the clip lever open and lock it in this position with the clip support byturning clockwise the black anodized aluminum knob in the bottom plate ofthe 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 thecell and rotate it together with the cell top back to the initial position (insidethe Faraday Cage). The quartz crystal sealed to the cell should be directedtoward you so that the contact pins extending from the crystal will not bedamaged by the clamp fixture. After the cell top, with the cell, is rotatedback into the Faraday Cage and the cell is fully supported by the bottom plateof the ROTACELL, carefully turn the cell clockwise until the crystal pinsslide onto the disk shaped contacting metal pads which are hot-pressed intothe clamp base block.

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

6. CRYSTAL-CELL ASSEMBLY

37

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

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

(4) Check if the cell is tightly positioned in the holder. If it is loose, press theclip to free crystal pins, and remove the cell from the holder. Adjust thebottom 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 openand lock it in this position with the clip support by turning clockwise theblack anodized aluminum knob in the bottom plate of the ROTACELL.

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

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

6.4. Final checks

(1) Check the assembly in order to avoid a short circuit across the contact platesin 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 thefrequency of oscillation.

7. ELECTRIC CIRCUITS

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7. ELECTRIC CIRCUITS

7. ELECTRIC CIRCUITS

39

WO and ROBUFFERS

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

SCALINGOP. AMPS.

TIMEBASE

COUNTERLOGIC

FREQUENCYMETER

f/VCONVERTER

ACTIVEFILTER

VOLTAGEOFFSET

OUTPUTFILTERS

DIGITALPANEL METER

V-out(M-out)

Δf-in

7. ELECTRIC CIRCUITS

40

ROREFERENCEOSCILLATOR

OPTICALISOLATION

FREQUENCYDIFFERENCE

ΔfBUFFER

WO and ROBUFFERS

Reference QC

Working QC inelectrochemical

cell

WOWORKING

OSCILLATOR

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

OPTICALISOLATION

ReferenceFrequencySelector

Ext. Freq. Ref.Input

Δf-OUT

f-OUT

7. ELECTRIC CIRCUITS

41

8. SERVICING NOTES

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8. SERVICING NOTES

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

9. WARRANTY

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WARRANTY

All our products are warranted against defects in material and workmanshipfor one year from the date of shipment. Our obligation is limited to repairing orreplacing products which prove to be defective during the warranty period. We arenot liable for direct, indirect, special, incidental, consequential, or punitive damagesof any kind from any cause arising out of the sale, installation, service, or use of ourinstrumentation.

All products manufactured by ELCHEMA Company are thoroughly testedand inspected before shipment. If ELCHEMA receives notice from the Buyer of anydefects during the warranty period, ELCHEMA shall, at its option, either repair orreplace 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 theoriginal 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 areexcluded from warranty.

THE WARRANTY SET FORTH IS EXCLUSIVE AND NO OTHERWARRANTY, WHETHER WRITTEN OR ORAL, IS EXPRESSED OR IMPLIED.ELCHEMA SPECIFICALLY DISCLAIMS THE IMPLIED WARRANTIES OFMERCHANTABILITY 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 difficultyand include the instrument model and serial numbers. Service date and shippinginstructions will be promptly sent to you. There will be no charges for repairs ofinstruments under warranty, except transportation charges. Estimates of charges fornon-warranty or other service work will always be supplied, if requested, beforework begins.

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CLAIM FOR DAMAGE IN SHIPMENT

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

SHIPPING THE INSTRUMENT FOR WARRANTY REPAIR

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

GENERAL

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

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