A device to obtain an estimate of the spectrum of a time-variable magn
etic field has been developed. The amplitude of each spectral componen
t of the magnetic field series is obtained by analyzing with a double
demodulation technique the signal generated from a flux-gate-like dete
ctor operating in open loop configuration. This device shows a sensiti
vity of about 1 mV/nT in the range from 0 to 300 Hz. For frequencies h
igher than 300 Hz the sensitivity decreases, and a correction factor t
hat depends on the transfer function of the electronic device must be
applied. The present device can be applied to environmental measuremen
ts, industrial applications, traffic control, and scientific research.
(C) 1995 American Institute of Physics.