Precision Characterisation of Current Transformers and Shunts in the Audio Frequency Range

This paper presents a technique to compare two current transformers, or a current transformer and ac current shunts, with an uncertainty better than 1 uA/A and 1 urad at audio frequencies. Examples of such a comparison at frequencies from 10Hz to 10kHz are given. Due to its low uncertainty, the described technique made it possible to accurately measure critical parameters such as common-mode dependence of a current transformer and impedance variation of current shunts with ac current applied.