An International Comparison of Thermal Converters as AC-DC Transfer Standards

The ac-dc differences of 4 sets of thermal current and voltage converters were determined at 40 Hz, 20 kHz, and 50 kHz with reference to the standards of the national metrology laboratories of the United Kingdom, Japan, the Soviet Union, and the United States. For each voltage and current range and at each frequency, the average ac-dc difference determined by each laboratory for the 4 sets differed from the average of all laboratories by less than 10 ppm.