Figure 3—The driver supplies a square wave to the sensor as well as a sync signal to enable the integrator input only when the drive coil is saturated. The Helmholtz coil is fed with an adjustable offset to compensate for the local static field (VR2), a programmable offset from the PSoC (R22), and the sensor feedback signal (R23). R22 and R23 should be ratio-matched to within 0.1%.