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