CURRENT DEVELOPMENTS IN ACCURATE AC-DC TRANSFER MEASUREMENTS

Recent improvements in commercial ac instruments have led to worldwide activities in the field of basic standards for ac-de transfer measurements. Current developments are discussed in this paper. The results obtained with the recently improved single junction and multijunction thermal converters and the ''fast reversed dc'' experiment show an agreement at the uncertainty level of 10(-7). New thin-film designs offer the possibility of low-cost mass production of highly accurate and sensitive multijunction thermal converter. Improved standards have been developed for the mV-, but also for the high-voltage ranges. At low frequencies the application of the D/A conversion technique for the transfer of de to ac seems to be advantageous.