Increased Accuracy for Resistance Measurements

The effect of power dissipation on the performance of four-terminal standard resistors has been investigated, using the direct-current-comparator ratio bridge. A theoretical analysis of a typical standard resistor has also been made, which indicates that the average temperature increase of the resistance wire in an oil-filled resistor is approximated by T - T = RI2[6(1-e0.001t)+1] and that the Peltier effect at the copper-manganin junctions may contribute errors of 1 to 10 parts per million of resistance for the lower-valued resistors. Recommendations are made for design and construction changes in standard resistors, which will improve the accuracy with which they may be used.