The Error Due to the Peltier Effect in Direct-Current Measurements of Resistance

The recent development of ac bridges for precise resistance determinations has brought on the not altogether unexpected discovery of significant differences between dc and ac measurements. In this article, we discuss one such difference, observed in germanium resistance thermometers, and show that it can be unequivocally ascribed to the Peltier effect, the dc measurement in this case being in error. This conclusion is based on a thermal model of the resistor which predicts accurately the magnitude and frequency variation of the observed effect, both for 2- and 4-terminal measurements. The applicability of this model to other devices is briefly discussed.