Improved AC–DC Current Transfer Step-Up With New Current Shunts and Potential Driven Guarding

The ac-dc current transfer standards at PTB have been improved in frequency and current range up to 1 MHz and 1 A using a newly designed transconductance amplifier. Up to 100 kHz and 10 A, the uncertainties could be dramatically reduced. Starting from the calculable quartz planar multifunction thermal converter at 30 mA, for currents up to 10 A, new shunts with small frequency and current level dependence and an improved measurement set-up are used