A simple direct-digitizer for Giant magneto-resistance based sensors

A Direct Digitizer suitable for Giant magneto-resistive (GMR) sensors is proposed in this paper. The proffered digitizer integrates a GMR sensor, in the form of a full-bridge, with a novel circuit based on enhanced dual-slope technique and obtains a linear digital indication of the magnetic field being measured. The scheme does not use a separate ADC for digitization. A detailed mathematical methodology of the scheme has been reported to validate the linear transfer relation of the proposed scheme. Simulation study of the proposed circuit has been performed and the results show that output-non linearity is as small as 0.004 %. Further, the performance is validated by experimentation with emulated and actual GMR sensor bridges and results are reported. Output is found to be linear with-respect-to the magnetic field and the worst-case error is within acceptable limits. The proposed scheme can be employed as a superior alternative to conventional (instrumentation amplifier) based interface circuits for GMR sensors.