Abstract: Sealing assemblies (16, 18, 20) are disclosed for isolating electronic circuitry (14) within a magnetometer (12) from the effects of water intrusion when the magnetometer is used under water. The electronic circuitry (14) is positioned within an inner cylindrical member (24) and the ends of the inner cylindrical member are sealed by RTV rubber plugs (50, 52). Passages (54) through the plugs permit signal cables to extend from the electronic circuitry to the surface. The compression of the resilient plugs seals against the cable and the inner wall of the inner cylindrical member. Interior O-rings (46, 48) seal between the exterior of the inner cylindrical member and the inner wall of an outer cylindrical member (62) to seal the annular space therebetween. Couplings (66, 68) are secured at each end of the outer cylindrical member (62) and accept nipples (70, 72). Caps (78, 82) are slid over the nipples.

Abstract: A conventional magnetometer produces an output signal (10) which comprises a series of pulses (12, 14, 16). Each of these pulses has a beat frequency maximum. These pulses are input to a comparator (50) which makes a comparison to a threshold voltage V.sub.0 to produce a bi-level detected signal at a line (62). The detected signal is input to an integrator (52) which produces a series of pulses (78, 80, 82) corresponding respectively with the magnetometer output signal pulses (12, 14, 16). The two states of the detected signal corresponding to positive and negative integration. The time period for the positive integration is proportional to the beat frequency maximum time width period for the corresponding magnetometer output signal pulse. Thus the integrated pulses (78, 80, 82) have an amplitude which is a measure of the maxima time width periods for the corresponding magnetometer signal pulses.

Abstract: A magnetic field detector for determining the presence of a magnetic field disturbance in the vicinity of the apparatus senses the difference in magnetic fields at two spaced-apart locations. A pair of field sensors, each including a body of polarizable liquid and a probing coil, are connected in series and provide an output signal that is produced in the coils by the free procession of the protons of the liquid bodies in the earth's magnetic field. A timer circuit controls a relay to alternately connect the magnetometer coils to a source of polarizing current during a polarizing period, and to detection circuitry during a listening period. The detection circuitry includes a high gain signal channel comprising a multi-stage, high input impedance preamplifier and a bandpass amplifier tuned to the frequency range of the signals generated in the probing coils.

Abstract: A magnetic field detector for determining the presence of a magnetic field disturbance in the vicinity of the apparatus senses the difference in magnetic fields at two spaced-apart locations. A pair of field sensors, each including a body of polarizable liquid and a probing coil, are connected in series and provide an output signal that is produced in the coils by the free precession of the protons of the liquid bodies in the earth's magnetic field. A timer circuit controls a relay to alternately connect the magnetometer coils to a source of polarizing current during a polarizing period, and to detection circuitry during a listening period. The detection circuitry includes a high gain signal channel comprising a multi-stage, high input impedance preamplifier and a bandpass amplifier tuned to the frequency range of the signals generated in the probing coils.