Design of high-precision calibration system for direct current-current transformer

The measurement accuracy of direct current-current transformer (DCCT) is one of the key factors influencing the output of high-precision direct current power supply. For the DCCT measurement accuracy is better than 1 × 10^-5, a calibration system designed by measuring resistance principle with a high accuracy direct current comparator (DCC) was presented. The system can achieve high-precision calibration of DCCT within the measurement range of 0-400 A, and the relative uncertainty of the system calibration is better than 1.1 ppm in the whole range. The accuracy and linearity of DCCT were tested to verify the accuracy of the whole calibration system, which can improve the current accuracy of the magnet power supply in the future. (authors)