AC-DC transfer measurements in the mV-range using discrete micropotentiometers

This paper describes the new primary standard for the ac-dc low voltage transfer at Inmetro, based on micropotentiometers with PMJTCs and commercial current shunts. The design of the new micropotentiometers is presented, followed by the build-down of the voltage scale into the mV-ranges and the uncertainty analysis. Finally, the results of an unofficial interlaboratory comparison between Inmetro and PTB, at 20 mV, are presented and discussed.