Continuous calibration of Rogowski coil current transducer

Rogowski coils (RC) intended for high-accuracy contactless current measurement ask for precise sensor geometry and specific conditions, such as a centered primary conductor. To release these constraints, we propose in this paper a recently patented continuous calibration system which features a reference conductor added coaxially to the primary conductor and a proportional-integral controller integrated in CMOS technology. The chip is mounted on a board with a precise shunt and a AC reference signal generator. The magnitude of this reference signal may exhibit slow variations, only its frequency needs to be accurate, which is a great advantage. The architecture of the chip is described as well as the experimental setup. Experimental results obtained with commercial flexible RC show that the sensor immunity to the conductor position, as well as the dispersion between several RC, is reduced to ±0.1 %, i.e. a 0.1 class measurement. In addition, the system may ensure an absolute calibration of the RC current transducer, avoiding any costly calibration procedure at the end of the sensor manufacturing.