y for same rest entirely with the user.
CAUTION
Use a QUIET TIME* of six seconds
or greater for all experiments.
*QUIET TIME is a function of the BAS 100A/B/W
and CV-50W. When using any other instrument
with the LCM, the cell should be connected at
the initial potential for six seconds before starting
the experiment. Table of Contents
Section 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2
Section 2. General Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3
User Updates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3
Technical Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3
Shipping Damage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3
Limited Warranty . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3
Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4
Section 3. Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5
Inspection of Shipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5
Parts of Low Current Module. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5
Power Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5
Environment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6
Installation of I-E Tansducer in Cell Stand . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6
Cable Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7
Analog Cable from BAS 100 Series, CV-50W, CV-27 to I-E Transducer . . . . . . . . . .
7
Analog Cable form I-E Transducer to Other Electrochemical Instrumentation . . . . . . .
9
I-E Transducer Control Cable from PA-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9
PA-1 Control Cable from BAS 100A/B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10
CV-27 Ground Cable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
11
Section 4. Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12
Front Panel Controls. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12
Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12
Remote/Local . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12
Gain nA/V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12
Multiplier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12
Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12
Cell Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13
Rear Panel Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13
I-E Transducer Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Cell Equilibration Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14
Automatic Operation with the BAS 100A/B/W . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14
Manual Operation with BAS Instruments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14
Operation with Potential Waveform Generator and Recorder . . . . . . . . . . . . . . . . . . . 18
Operation with BAS C2 and C3 Cell Stands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
19
Use with Home-Built Faraday Cage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
19
Table of Contents
i Section 5. Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
20
Cautions and General Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
20
Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
20
Service Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
22
Appendix"Voltammetric Microelectrodes." Jonathon O. Howell,
Current Separations
8:1/2
(1987) 2.
Table of Contents
ii Section 1. Introduction
Microelectrodes (electrodes with micrometer diameters) are commonly employed for studies
in small volumes, in resistive solutions, and at high speeds (see Appendix). Because of their
small size, low nA or even pA currents are typically generated in these studies. Most
general-purpose commercial electrochemical instruments (including the 100B/W, CV-50W,
and CV-27) are designed to measure current at levels (100 nA - 100 mA) that would
normally be generated at conventional electrodes with a diameter exceeding 1 mm. The Low
Current Module (LCM) includes an amplifier which may be used to adapt existing
instrumentation for microelectrode and other applications requiring the measurement of
current less than 1 microampere. The LCM is available in two versions for use with either
the C2 or C3 Cell Stand.
Figure 1. This cyclic voltammogram of 2 mM ferrocene in 0.1 M TBAP/acetonitrile at a 0.6 �m platinum electrode illustrates the
magnitude of current normally seen with small diameter electrodes. Without the shielding and amplification of the C2 or C3 and
low current accessory, this voltammogram would also include noise and interference.
Great care was undertaken during the development of the Low Current Module to maximize
the signal-to-noise ratio during low current measurements. This was accomplished by
separating the electronics of the LCM into two boxes. One box contains the potentiostat and
the current-to-voltage (I-E) transducer, while the other contains a second gain stage, filters,
power supply, and control circuitry. The critical part of the electronics is in the first box,
which mounts inside a C2 or C3 cell stand. The cell leads and cell are enclosed in a
Faraday cage to shield the cell from line frequency and other external electrical interference.
This shielding is necessary when measuring submicroampere currents. Since the electronics
are adjacent to the cell, the cell lead length can also be minimized. A short cell lead
minimizes stray capacitance, which increases frequency response. The signal from the I-E
transducer is then transferred into the second box where it is filtered through a
second-order, low-pass, Bessel filter and further amplified if necessary.
Section 1. Introduction
1 When the LCM is set for remote operation, it can be automatically controlled by the BAS
100A/B/W. The 100B/W connects and disconnects the cell from the electronics and sets the
gain and filter to settings appropriate to the time scale of the experiment. When used with
the CV-50W and CV-27 Voltammograph in manual mode, all functions are controlled by the
front panel knobs and switches.
This manual describes the installation and operation of the Low Current Module and
provides an introduction to the properties of microelectrodes. Some of the theoretical and
practical background of the voltammetry experiment as well as the physical manipulation of
the switches are discussed. An understanding of the limitations and the advantages of the
techniques is imperative to form the correct conclusions from the resulting data.
Specifications
Potentiostat
Compliance voltage: �12
Maximum current available: 12 �A
Current-to-Voltage Output
Range: 10 pA/V - 1 �A/V sequence in decades
Maximum measurable current: 12 �A
Frequency response: up to 25 KHz
Front Panel Controls
Remote-local control switch
Power switch
Gain: 1, 10, 100, and 1000 nA/V
Gain multiplier: X1, X0.1, and X0.01
Filter (second-order, low-pass Bessel): cut-off
frequencies of 0.5, 5, 50, 250, 2.5 K, and 25 KHz
Cell mode: on/off/test
PA-1 Rear Panel Connectors
CorComm power connector
BAS 100A/B accessories control connector
Low current input connector to control I-E transducer
I
out
Common
Earth ground
I-E Transducer Rear Panel
Control cable input
LEMO analog connector
I-E Transducer Front Panel
Cell lead cable (red/auxiliary, white/reference,
black/working)
Section 1. Introduction
2 Section 2. General Information
User Updates
To receive product update news and valuable information related to this and other BAS
products, fill out and return the BAS Warranty Enrollment Card shipped with your Low
Current Module. We would like to know who you are and how we can meet your
electrochemical analysis needs.
Technical Changes
BAS may make technical changes to improve the instrument. Improvements affecting use or
maintenance will be described in supplementary pages to this manual.
Shipping Damage
Damage to any part of the LCM during shipping should be reported immediately to the
freight handler and BAS Customer Service. Unless other arrangements have been made, the
freight handler (shipper) is responsible for all damage or breakage to the instrument and
parts.