Development of a Current Sensor Based on a Magnetic Fluid Magnetic Bridge

Demands for dc current sensors have recently been increasing. We developed a hysteresis-free current sensor based on a magnetic bridge by using magnetic fluid as a core material, which is super-paramagnetic and has no magnetic hysteresis. In the experiment, the core size was 42 mm in outer diameter, 28 mm in inner diameter, and 3.5 mm in height. The sensor became saturated at ±200 A input current, but no hysteresis was observed throughout the whole range of measurement. In a measurement range of ±20 A, the sensitivity was 0.603 mV/A, the linearity error was ±0.7 %, and the temperature error characteristics were -0.2 %/°C from 0 °C to 30 °C. This hysteresis-free current sensor would be useful in energy-efficient power systems to enable accurate current monitoring, especially in dc power-distribution systems.