Recent improvements to an automated precision wide-band AC-DC transfer standard

Precision voltage measurements have historically been made by ac/dc thermal transfer techniques which require time-consuming tedious manual efforts by an experienced metrologist. This measurement process has been automated successfully without sacrifice of accuracy. AC /DC transfers requiring approximately 30 to 40 s for each voltage point have been achieved with uncertainties of 20 to 30 ppm and standard deviations in the order of 3 ppm. Precision-automated transfer measurements reduce operator skill requirements and make use of IEEE-488 programmability to enable the latest automated ac/dc Transfer Standards to be used in computer-aided calibration systems. Some of the circuit techniques and methodology used in automating programmable ac/dc wide-band transfer standards are described in this paper.