The Testing of Potentiometers (Classic Reprint), Wenner Frank

The test therefore consists in making such measurements as are necessary for the determination of the ratio of Re to R s for all settings of both R, and R S.

When a potentiometer is used in conjunction with a standard resistance and standard cell for determining the current or power, the measurement with the potentiometer is in reality that of a potential difference. The test just referred to is therefore all that is required. The resistance of the coils is not always accurately adjusted, nor does it remain constant but changes somewhat with time. The greatest change occurs within one year after construction and may amount to as much as several hundredths per cent. Later the changes seldom amount to as much as one hundredth per cent during a year, in well-constructed potentiometers. Therefore potentiometers which are to be used in measurements of high precision 1 should be calibrated occasionally, especially during the first few years. If this is done and the corrections applied, errors on account of lack of adjustment of the coils or on account of changes in their resistance can be eliminated.

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