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Geophysical InstrumentsGeometrics model G-856 is a proton precession magnetometer with a clock and sufficient memory to store 1024 readings plus the time at which each measurement is made. This device measures the magnitude of the geomagnetic field to a precision
The E.G.& G. Geometrics model G-856 is a proton precession magnetometer with a clock and sufficient memory to store 1024 readings plus the time at which each measurement is made. This device measures the magnitude of the geomagnetic field to a precision of 0.1 gamma (the typical field strength in northwest Ohio is about 55,000 gammas). Measurements stored in memory can be recalled to the display but are usually downloaded to a computer.
Most materials are induced by the geomagnetic field to take on a weak magnetism of their own. Magnetic field lines caused by a magnetized object are added (vector sum!) to the geomagnetic field, thus distorting the field. This perturbation is called an anomaly. The shape and amplitude of an anomaly depends on the location and magnetic moment of the object.
Magnetometer surveys are frequently useful in mapping concealed contacts between igneous and sedimentary rocks. Magnetometer surveys have also proven useful in locating buried steel drums, underground storage tanks, and cased wells that have been buried. At archaeological sites, magnetic anomalies have been associated with trash pits and fire pits.