Hysteresis Compensation Based on Controlled Current Pulses for Magnetoresistive Sensors

This paper presents a novel hysteresis compensation method for increasing the measurement accuracy of magnetoresistive (MR) sensors such as anisotropic magnetoresistance (AMR), giant magnetoresistance (GMR), and tunnel magnetoresistance (TMR) sensors. A coil consisting of one winding is processed on top of the sensor element. This configuration allows short current pulses (positive and negative) to generate a defined magnet field, which should be much stronger than the field to be measured. In this case, the MR sensors can always be kept in the same magnetic loop (major loop) during the measurement cycle. By demodulating or averaging the output signal of the sensor, the influence of the sensors hysteresis can be largely reduced. A mixed signal circuit consisting of a field-programmable gate array, analog-to-digital converters and analog switches is used to generate the pulses. AMR, GMR, and TMR current sensors are chosen as examples in the experiment. Current measurements with and without controlled magnetic field pulse are compared. A hysteresis reduction to nearly 20% of the original value, by using the novel hysteresis compensation method, is reached.