Magnetic field intensity measuring device with frequency change indication

Claim 1

A magnetic field measuring device adapted for being connected between first and second potentials of a direct current electrical power source and for providing a signal whose frequency of oscillation is indicative of the intensity of external magnetic fields sensed by said device, said detector comprising: first and second nonlinear amplifiers each of which is comprised of a P-channel field effect transistor and an N-channel field effect transistor connected in an inverter configuration such that the drains of said transistors form a first common electrical junction and the gates of said transistors are connected in parallel to form a second electrical junction; a core comprised of magnetic material, said core being straight in shape, so as to produce directivity of measurement of said magnetic field along the longitudinal axis of said core; and a coil of wire encompassing said core having one end connected to the first common electrical junction of said first nonlinear amplifier and to the second common electrical junction of said second nonlinear amplifier, and having the other end connected to the first common electrical junction of said second nonlinear amplifier and to the second common electrical junction of said first amplifier; wherein when the source of said P-channel field effect transistor in each of said amplifiers is connected to said power source so that said first potential is applied thereto, and the source of said N-channel field effect transistor in each of said amplifiers is connected to said power source so that said second potential is applied thereto, substantially the first and second potentials are applied across said coil with the direction of current through the coil reversing at a switching rate which is indicative of the intensity of external magnetic fields sensed by said device.