AN EARTH'S FIELD MAGNETOMETER THAT UTILIZES THE FREE PRECESSION OF PROTONS

This paper describes the instrumentation of a new type magnetometer that measures the earths field by measuring the free precession frequency of the protons in water. Results obtained indicate that with the present equipment configuration the earths magnetic field can be measured to within 0.00002 gauss out of 5000 times 10 to the -5th power gauss on an absolute basis and that changes of 14 times 10 to the -5th power gauss can be detected. This technique probably represents the most accurate method presently available for measuring the absolute value of the earths magnetic field. Further, changes of much less than 14 times 10 to the -5th power gauss could be detected by this method if it were necessary or desirable simply by increasing the frequency of the crystal controlled source in the counting system. Possible applications include use as a station magnetometer for a magnetic observatory, use for magnetic surveying or prospecting, and use in harbor defense and air anti-submarine work.