Low I Range Dc Calibration - Gamry Instruments Reference 3000 Operator's Manual

Caution:
cell. Your Reference 3000 was shipped with a Calibration Cell, which includes a 2 kΩ, 0.05% accurate
resistor. After calibration, please place this Calibration Cell in a safe place where you can find it if your unit
requires recalibration.
If you do need to recalibrate and you cannot find your Calibration Cell, you can perform DC Calibration
using a different 2 kΩ resistor. Its power-rating is unimportant. Some performance checks in the calibration
process may fail if the resistors inaccuracy exceeds 0.2% (4 Ω).
We do not recommend AC Calibration with any resistor other than the one on the Calibration Cell. The
Calibration Cell was designed to separate the working electrode leads from the counter and reference
electrode leads. If you perform AC Calibration without adequate separation between these leads, you will
see a phase-shift in your high-frequency EIS data. 1.4 pF of stray capacitance across a 2000 Ω resistor
causes a 1° phase-shift at 1 MHz.
Enclose the resistor used for calibration in a Faraday shield during the calibration process. Connect the Faraday
shield to the black lead on the standard cell cable. A Faraday shield suitable for calibration is included in every
Reference 3000 shipment.
Earth-grounding the Reference 3000 is also recommended during calibration but is not essential.
Potentiostat calibration is only required infrequently. Recalibrate your Reference 3000 under the following
circumstances:
It has been about one year since your last calibration.

Your potentiostat has been serviced.

You notice breaks or discontinuities in the data-curves recorded with your system.

The system is being run in an environment that is very different from the previous operating

environment. For example, if the Reference 3000 was calibrated at 15C and you are now operating it
at 30C, you should recalibrate.

Low I Range DC Calibration

The standard Reference 3000 calibration is performed with the cell leads connected to a 2 k resistor. During
the calibration procedure, DC current-range offsets are recorded with the cell switch turned off. A DC current
measurement is made on each of the eleven current ranges in the Reference 3000. The measured current on
each range is the sum of current contributions from:
The input current of the I/E Converter input amplifier,

The input current of the Working sense input amplifier,

The input current of the Reference input amplifier,

The input current of a Counter Sense input amplifier,

Current leakage in the cell switch.

In most real-world experiments, the cell is turned on, and the I/E converter does not measure the last three
terms listed above. These currents still exist, but they are generally sourced by the low-impedance counter-
electrode lead. During Low I DC Calibration the first two terms are directly measured in order to improve pA
accuracy of the instrument.
Calibration – Low I Range DC Calibration
The standard Reference 3000 calibration calls for an external resistive dummy
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