A bus programmable autobalancing AC/DC thermal transfer standard

Precision ac voltage measurements use transfer techniques which compare the rms heating value of the unknown waveform to an identical dc voltage which is readily measured. Recent developments in thermoelement technology and the development of more accurate digital ac voltmeters and ac voltage calibrators have upgraded ac measurement capability to the 80-ppm uncertainty range. NBS traceable calibration of these instruments is now possible through the development of the new IEEE 488 programmable autobalancing ac/dc transfer standard. The techniques which permit automated computer-aided ac measurements to 100 MHz with uncertainties to 30 ppm are described in this paper.