Calibration of ultrastable low-noise current amplifiers without direct use of a cryogenic current comparator

摘要

The established calibration of the transresistance of the ultrastable low-noise current amplifier (ULCA) directly involves a cryogenic current comparator (CCC). Here, we present an alternative approach based on a calibrated set of three resistors and three digital voltmeters. This approach was experimentally verified for a two-channel ULCA with nominally 1 G omega transresistance using PTB's travelling 12 bit CCC setup in an on-site comparison at METAS. Series of interleaved experiments included calibrations of the input and output stages of two different ULCA channels. The consistency found between the conventional calibration with PTB's CCC and calibration with METAS' set of three resistors-each traced to the quantum Hall resistance with METAS' CCC-confirms that the alternative traceability chain provides valuable results. If the standard resistors are calibrated without using a CCC, the new method even opens the possibility to calibrate the ULCA without any CCC in the traceability chain involved, however, typically at the expense of increased uncertainty.