Avoiding Measurement Errors

Sources of Errors

There are many possible sources of errors in an electrochemical cell set-up, but only a few bother us repeatedly.

About the hen and the egg

- To establish the desired potential at a working electrode, a certain current has to be passed from the counter electrode to the working electrode.

- The current is a function of cell resistance and cell voltage.

- as long as the desired potential is not detected, the potentiostat feeds current as hard as possible to establish the potential.

So, it is clear that any loss of the feedback signal, i.e. the voltage detected by the reference electrode, results in a maximum of current which the potentiostat can deliver. This may  spoil the electrolyte, and destroy even your electrodes.

Rule 1

Care for a good contact between reference electrode and working electrode. The higher the resistance between working electrode and reference electrode, the higher is the noise.

Rule 2

Very high resistance in the salt bridge may produce loss of any control.

Rule 3

Make sure the compliance voltage of your instrument is high enough. If it is close to the limits, try to keep your electrodes close together.

Rule 4

Check the temperature of your cell when the absolute values of the current are essential.

Rule 5

Keep the Haber Luggin capillary close to the working electrode (1-2 mm) - otherwise ohmic drop may affect the measurement.

 Rule 6

When high current shall pass the working electrode, it is essential to feed current cable and the working electrode's  potential sense cable separately to the working electrode. Otherwise, potential drop in the current cable would lead to wrong potential measurement.

Bank Elektronik -

Intelligent Controls GmbH

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D-35415 Pohlheim


Tel. +49 - 6403 - 60 98 60

Fax  +49 - 6403 - 60 98 622

e-Mail: info [at] bank-ic.de


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