Integrated front-end for on line continuous calibration of Rogowski coil current transducer

The Rogowski coil is a traditional current-to-voltage transducer. To use it for high-accuracy measurement of low frequency AC current, it is necessary to have a very precise sensor geometry and very specific conditions, such as a stable temperature and a centered primary conductor in order to minimize errors. Conversely, it is also possible to compensate for these errors by using a sensor calibration. This paper presents a new continuous calibration system for Rogowski coil current transducer (RCCT). It features a reference conductor added close to the primary conductor and a calibration circuit which has been integrated in CMOS technology. First experimental results obtained with a homemade RCCT show that we drastically improve the immunity of the sensor to the primary conductor position with an error below ±2 % when the calibration is active against -8% to +4% without calibration. Limitations of the method are also discussed.