A digital fluxgate magnetic sensor interface using sigma-delta modulation for weak magnetic field measurement

This paper presents a weak magnetic field measurement system using micro-fluxgate sensors and a sensor signal processing technique using the sigma-delta modulation in the negative feedback loop. The feedback of low-pass filtered bitstream output of a sigma-delta modulator to the magnetic field improves system linearity, hysteresis and stability. The third-order noise shaping can be obtained in the digital output bit-stream by the use of an integrator in the loop. Earth´s magnetic field is successfully measured. The non-linearity error is less then 0.4 % in the range of ± 100 μT.