Accession Number : ADD013009

Title :   Free Nuclear Precession Gradiometer System.

Descriptive Note : Patent,

Corporate Author : DEPARTMENT OF THE NAVY WASHINGTON DC

Personal Author(s) : Hinton,George F

Report Date : 08 Oct 1985

Pagination or Media Count : 5

Abstract : This patent discusses a free nuclear precession gradiometer which uses a fluid sample surrounded by a coil the fluid sample containing one or more nuclear species which display a magnetic moment. Current in the coil polarizes the nucleii, which when the current is abruptly terminated precess coherently about the earth's magnetic field. The exact frequency generated is a precise measure of the absolute value of the earth's magnetic field. The signal is in the form of a damped sinusoid with the rate of decay being a function of gradients in the ambient magnetic field. Two vector magnetometers are mounted rigidly on the sensor at the right angles to each other and the earth's magnetic field. A servo system continuously orients the sensor in a two-axis gimbal system to reduce the output of the vector magnetometers to zero. The instrument is polarized, a counter is triggered to make the frequency measurement, and the signal is analyzed by determining the average amplitude of the signal over a precise interval of time. The result is simultaneous measurement of total intensity and total gradient.

Descriptors :   *PATENTS, *GRADIOMETERS, MAGNETIC FIELDS, GEOMAGNETISM, MAGNETIC MOMENTS, INTERVALS, PRECISION, TIME, DECAY, RATES, SERVOMECHANISMS, AMPLITUDE, SIGNALS, FREQUENCY, MEASUREMENT, PRECISION, SYNCHRONISM, SIGNAL PROCESSING

Subject Categories : Geomagnetism
      Test Facilities, Equipment and Methods

Distribution Statement : APPROVED FOR PUBLIC RELEASE