SPECTRAL ESTIMATION FOR A MAGNETOSTRICTIVE MAGNETIC-FIELD SENSOR

Recently there has been increasing concern regarding the effects of lo w-frequency magnetic Belds on humans and livestock. A portable magneto meter is essential for monitoring the field dose encountered. There ar e some devices currently available for this purpose which use the indu ced EMF technique. The field sensitivity for these devices depends on the number of turns of coil used. This limits the minimum size of devi ces with reasonable performance. The magnetometer considered in this p aper overcomes this size limitation by using a highly magnetostrictive material, Terfenol-D, as the magnetic field sensor. The primary focus of this paper is to determine the magnetic field spectral characteris tics using digital signal processing. A survey of spectral estimation techniques are presented, followed by their application to the Terfeno l-D magnetic field signal. The estimators are compared using data obta ined from a magnetometer hardware prototype. Using these methods it wa s possible to detect signal for a field strength of 20 milligauss.