The application of the current-comparator technique in instrumentation and measurement equipment for the calibration of non-conventional instrument transformers with non-standard rated outputs

An overview of the development of instrumentation and measurement techniques at the National Research Council of Canada, based on current comparator technology, for calibration of nonconventional instrument transformers with nonstandard rated outputs, is presented. The instruments include: (1) a wide-dynamic-range transimpedance amplifier for operation of input currents from 1 A to 1000 A with means for modifying the in-phase and quadrature components of the output voltage (rated 10 V) within a ±10% range; (2) a high-voltage high-current transconductance amplifier with output current ranges of 10 A, 100 A, and 1000 A; and (3) a voltage ratio standard also with means for modifying the in-phase and quadrature components of the output voltage (rated 100 V) within a ±10% range. The current comparator technique is used to obtain accuracies of better than 20 parts per million in both magnitude and phase of the associated outputs of these instruments