Design, development and performance evaluation of GMR-based current sensor for industrial and aerospace applications

The article presents the development of an open-loop current sensor using indigenous multilayered giant magnetoresistance (GMR-ML) technology. The proposed current sensor consists of a magnetic core with an air gap, a GMR sensor chip, and a bias magnet. A GMR chip is biased with a permanent magnet to obtain linear bipolar output characteristics. The GMR chip measures the magnetic field produced in the air gap as a result of the current flowing through a conductor. The sensor design and characteristics were optimized and verified using both simulation and experiments. Several prototypes were fabricated and tested for the current range of ± 25 A. Experimental results indicate the sensitivity of the order of 0.165 mV/V/A with the temperature dependence of the sensitivity - 0.28 %/°C and bandwidth of 100 kHz. The fabricated prototypes were further compensated for temperature-dependent drift in sensitivity and offset in the temperature range of - 25 °C to 85 °C. The compensated sensor exhibits a sensitivity of 80 ± 0.5 mV/A with the temperature dependence of the sensitivity of 0.005 %/°C. The change in offset voltage of compensated sensor was less than 10 mV across the temperature range. The compensated prototype sensor shows a total output error of less than 1 % over the operating temperature range. Further, the performance of the sensor was evaluated for aerospace applications and compared with the existing current sensor. The comparative data shows an equivalent performance during the test.