A Study of Thermal Effect on High-Current Standard Resistor

This study investigates the thermal effect on the high-current standard resistor (0.01 Ω) for the high direct-current (DC) source calibration. The resistance values measured by the Volt-Ampere method are shown as a function of ambient temperature and the applied current times. The full bias of the DC current limit (100%) of the resistor exposes a large change of resistance for both using and without using cooling fans. By using cooling fans according to the manual, the increasing rate of resistance decreases and becomes stable with a settling time >90 s for the bias DC current of 100% of the limit, leading to the suggestion of the specified period before measurement. The difference of resistance changes for the bias current of 10%, 50%, and 100% of the current limit are 1, 26, and 73 μΩ/Ω, respectively. It indicates that active cooling should be used seriously during high current bias through the standard resistor. The measurement results can be a guideline for improving the accuracy of the calibration process.