AUTOMATIC MEASUREMENT AND CALIBRATION OF DC CURRENT RATIO ERROR

Abstract

DC current ratio error is an essential measurement performance of DC current ratio instrument, for example, DC current comparator, DC current transformer and DC current sensor. Error determination contributes to the instrument rational use. Based on the principle of secondary differential current measurement, self-calibration method, equal-ratio calibration method and stage-connection equal-ratio calibration method were put forward according to the characteristics of different calibrated instruments. Then, the actual value and error of DC current ratio were available. Meanwhile, circuit diagrams, calibration process and examples were provided; measurement uncertainty was evaluated. The result shows that the proposed methods meet the calibration requirements of DC current ratio instruments; the expanded uncertainty for the 1 A: 1 A～ 1000 A: 0.5 A ratio is 1.7×10-8～8.4×10-6. The automatic measurement program can effectively improve the work efficiency.