TECHNICAL
MANUAL
ELECTROCHEMICAL
QUARTZ CRYSTAL
NANOBALANCE
SYSTEM EQCN-900/F
ELCHEMA
P.O. Box 5067
Potsdam, New York 13676
www.elchema.net
Tel.:
(315) 268-1605
FAX: (315) 268-1709
TABLE OF CONTENTS
1. INTRODUCTION .........................................................................................
2
2. SPECIFICATIONS ........................................................................................
4
3. CONTROLS ..................................................................................................
3.1. Front Panel .....................................................................................
3.2. Back Panel .....................................................................................
3.3. Faraday Cage: Side Panel .............................................................
3.4. Faraday Cage: Internal Panel ........................................................
7
7
13
16
19
4. OPERATING INSTRUCTIONS ...................................................................
4.1. Inspection .......................................................................................
4.2. Precautions .....................................................................................
4.3 Faraday Cage .................................................................................
4.4. Grounding ......................................................................................
4.5. Thermal Sensitivity .......................................................................
21
21
21
22
22
23
5. INSTALLATION ..........................................................................................
5.1. Initial Set-up ..................................................................................
5.2. Power ON Checks ..........................................................................
5.3. Connections to a Potentiostat and Electrochemical Cell ..............
5.4. Testing Experiment with Real Cell ON ..........................................
5.5. Quartz Crystal Immittance Measurements ....................................
5.6. Other Utilities (Optional) ..............................................................
24
24
26
27
28
29
31
6. CRYSTAL-CELL ASSEMBLY ...................................................................
6.1. Mounting Quartz Crystals .............................................................
6.2. Assembling Piezocells in ROTACELL holder .............................
6.3. Disassembling Piezocells from ROTACELL holder ....................
6.4. Final Checks ..................................................................................
33
33
33
34
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/desorption
metal/alloy plating
surface oxidation
corrosion and corrosion protection
etching
heterogeneous polymerization
ion ingress to (or egress from) ion exchange films
oxidation/reduction of conductive polymer films
intercalation
coadsorption and competitive adsorption
moisture accumulation (from gaseous phase)
etc.
2
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.
3
2. SPECIFICATIONS
2. SPECIFICATIONS
Measurement Functions
(1) EQCN:
(2) QCI:
(3) F/V-C:
Electrochemical Quartz Crystal Nanobalance,
Quartz Crystal Immittance measurements,
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) .....................................
Frequency Shift (analog) .............................................
Frequency Shift Linearity ............................................
Mass Change ...............................................................
Mass Change Linearity ...............................................
Extended Linearity .....................................................
Mass Change Sign .....................................................
Overload Indicator .....................................................
0 to 500,000 Hz
-100.0 to +100.0 kHz,
-10.00 to +10.00 kHz,
-1.000 to +1.000 kHz,
-100.0 to +100.0 Hz
0.02 % of reading + 0.05 % FS
-100.0 to +100.0 μg,
-10.00 to +10.00 μg,
-1.000 to +1.000 μg,
-100.0 to +100.0 ng
0.02 % of reading + 0.05 % FS
10 % over nominal range
+ for fWO < fRO
- for fWO > fRO
(Δm > 0, mass increase)
ca. 3 % over nominal range
Resolution
Frequency Difference: ................................................
Mass Change: .............................................................
4
0.1 Hz (analog)
0.1 ng (analog)
2. SPECIFICATIONS
Measurement speed
Mass change: ................................................................
Frequency shift: ............................................................
IQC, VQC, : ................................................................
30 s per point (max)
with Filter OFF
30 s per point (max)
with Filter OFF
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 (φ, PD-OUT): ........................... 45 deg/V
(i.e. -90 deg  -2 V,
+90 deg  +2 V)
Calibration:
IQC, φ: ............................................................. software
VQC, m, f: ........................................................ hardware
Voltage to Mass Change Ratio: ...................................
Voltage to Frequency Shift Ratio: ...............................
RANGE
(μg or kHz)
100.0
10.00
1.000
0.100
10 V per nominal range (Mass mode)
10 V per nominal range (Frequency mode)
MASS CHANGE
FREQUENCY SHIFT
0.100 V/μg
1.000 V/μg
10.00 V/μg
100.0 mV/ng
0.100 V/kHz
1.000 V/kHz
10.00 V/kHz
100.0 mV/Hz
Mass and Frequency Shift:
Extended linearity: .........................................
Offsets:
coarse: ...............................................
fine: ...................................................
Calibration: ....................................................
10 % over nominal range
0 to 90 μg or 90 kHz (approx.)
0 to 900 ng or 900 Hz (approx.)
hardware
Recorder Outputs
Analog Output Voltage Ranges:
Mass Change (V-OUT): ..................................
Frequency Shift (V-OUT): .............................
-10 to +10 V (MASS output mode)
-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: ................................................
5
0 or variable (0 to ca. 900 ng)
2. SPECIFICATIONS
Frequency Shift: ............................................
Quartz Crystal a.c. Current (iQC-OUT): ........
Quartz Crystal a.c. Voltage (VQC-OUT): ......
Phase Shift (PD-OUT): .................................
Calibration:
IQC, φ: ...........................................................
VQC, Δm, Δf: ..................................................
0 or variable (0 to ca. 900 Hz)
software
0V
software
software
hardware
Operating Parameters
Working QC Resonator Frequency: ...........................
Reference Crystal Frequency: .....................................
Power Supply: .............................................................
Dimensions: Instrument ........................................
Faraday Cage ............................. ......
10 MHz band
10.000 MHz (internal),
9.9 to 10.1 MHz (external, TTL/CMOS)
110/220 V, 50 - 60 Hz
4.5H x 14.5W x 15D, inch
14H x 12W x 11D, inch
Typical Measurement System Components
Model EQCN-900F
Model EQCN-900F-2
Model EQCN-900-3
Model EQCN-906
Model DAQ-616SC
Model PS-605E
Model RTC-100
Electrochemical Quartz Crystal Nanobalance Instrument
Faraday Cage
Remote Probe Unit (mounted on back of Faraday Cage)
Frequency Scanning Generator
Data Logger and Control Processor System
Potentiostat/Galvanostat
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 Thermostat
Model THERM-3
Temperature Controller
Model TSR-100
Temperature Probe (solid state, teflon coated)
Model STIR-2
Stirrer
Model 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/Galvanostat
Electrodes
Wide selection of quartz crystal working electrodes with Ag, Au, Al, Cr, Cu,
Fe, Ni, Pt, and Zn coatings
6
3. CONTROLS
7
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
8
3. CONTROLS
ELCHEMAF
Figure 1.
Front panel view of the Model EQCN-900F Electrochemical Quartz
Crystal Nanobalance with immittance measurement unit (QCI).
9
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. ATTENUATION
Rotary 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. POLARITY
Two 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. FUNCTION
OUTPUT 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 VOUT 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
10
3. CONTROLS
when 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 RANGE
RANGE 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. OFFSET
Two 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 readjust 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 masspotential 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 DPM
Digital Panel Meter displaying, in Hz, the frequency difference between the
frequency of the working quartz crystal and the frequency of a reference oscillator
11
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. OVERLOAD
Red LED activated when the measured mass change (frequency shift) exceeds the
actual V-OUT RANGE by ca. 3 %.
13. ATTENUATION INDICATORS
Green LED's indicating the iQC sensitivity selection.
14. FILTER INDICATORS
Green 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 INDICATORS
Green LED's indicating the MASS RANGE selection.
Other Controls
16. FILTER
The 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
12
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. POWER
Main power switch. The switch is illuminated when the POWER is ON.
13
3. CONTROLS
3.2. BACK PANEL
1. 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.
14
3. CONTROLS
15
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. CHASSIS
Banana 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 socket
HP 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 switch
Power 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.
16
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 IN
BNC 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. IN
BNC 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-OUT
BNC 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 ΔFOUT should be connected to the ΔF-IN BNC input on the back panel of the Nanobalance
Instrument EQCN-900F.
17
3. CONTROLS
1
RE
CE
2
WE
3
4
F-SCAN
IN
8
Float.
GND
EXT. REF.
INT.
F-REF
9
EXT.
5
IN
F-OUT
OSC.
INT.
EXT.
7
10
F-out
6
SPLY
11
I/O
12
Figure 3. View of side panel of the Faraday Cage.
18
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 toggle
Toggle 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 toggle
Toggle 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 toggle
Three-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.
19
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.
20
3. CONTROLS
1
REF
2
CE
4
3
EQCN
AIR
SOLN
QCI
5
AIR
SOLN
6
Figure 4. View of the inside panel of the Faraday Cage.
21
4. OPERATING INSTRUCTIONS
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. OPERATING INSTRUCTIONS
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
4. OPERATING INSTRUCTIONS
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 EQCN900F 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 RTC100) 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:
Amplitude:
Offset:
Start Frequency:
Stop Frequency:
Sweep Time:
square wave
5 Vp-p
0V
9.940 MHz
10.060 MHz
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
MHz
y:
|Y|
Y modulus
mS
z
fi
phase shift
deg
(13)
In QCI program, set
Notebook as follows:
variable
f
|Y|
fi
the plot scale on the SCALE page of the Tabbed
units/V
1
1
45
min
-105
-500
-500
max
105
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-toVoltage 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
INDICATOR
POSITION
CONSTANT
NUMBER
ms
_____________________________________________________
0
none
none (all OFF)
1
10
1
2
40
2
3
80
3
4
200
4
5
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.
35
6. CRYSTAL-CELL ASSEMBLY
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
6. CRYSTAL-CELL ASSEMBLY
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
7. ELECTRIC CIRCUITS
38
7. ELECTRIC CIRCUITS
TIME
BASE
COUNTER
LOGIC
f-in
SCALING
OP. AMPS.
VOLTAGE
OFFSET
OUTPUT
WO
and RO
ACTIVE
FILTER
FILTERS
BUFFERS
f/V
FREQUENCY
METER
FIGURE 6.
CONVERTER
DIGITAL
PANEL METER
Block diagram of Model EQCN-900F,
converter unit.
39
the nanobalance
V-out
(Mout)
7. ELECTRIC CIRCUITS
Ext. Freq. Ref.
Input
OPTICAL
ISOLATION
Reference QC
Reference
Frequency
Selector
RO
f
BUFFER
REFERENCE
OSCILLATOR
fOUT
FREQUENCY
DIFFERENCE
WO and RO
BUFFERS
WO
WORKING
OSCILLATOR
OPTICAL
ISOLATION
Working QC in
electrochemical
cell
FIGURE 7. Block diagram of electronic circuits of the nanobalance unit
mounted in the Remote Probe Unit in Faraday Cage.
40
f-OUT
7. ELECTRIC CIRCUITS
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.
42
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 Warranty
A. 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.
43
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:
ELCHEMA
Customer Support
P.O. Box 5067
Potsdam, NY 13676
Tel.: (315) 268-1605
FAX: (315) 268-1709
44