Power line field interference rejection for magnetic sensors

摘要

The discriminator consists of two major parts; a nonlinear filter for low level rejection, and inhibiting logic for high level rejection, of ac magnetic fields. The nonlinear filter approximately halves the frequency characteristics of a particular class of signals, while at the same time doubling the frequency of normal interfering signals. The inhibiting logic uses the known in-phase relationship to sense and reject even very large time dependent interference. However, spatially variant signals observed from near field relative motion of two orthogonal magnetic sensors with respect to a ferro-magnetic object have a near quadrature relationship that permits signal recognition even when of less amplitude than the interference.