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Digital, Recording Vehicle-borne Magnetometer

Digital, Recording Vehicle-borne Magnetometer

Geophysical Research Institute. Armidale, Australia

1978

Method: Magnetics

Description

The rapid measurement rate capability of the caesium magnetic sensor demanded not just a method for automatically recording both the magnetic field measurement and the position at which each measurement was acquired, but it also demanded digital recording of this data and by 1978 this was becoming available. A vehicle-borne system was seen as an efficient means to acquire detailed magnetic data on a regional or mineral exploration scale. Benefitting from experience with the archaeological odometer, an electronic switch was added to the tail-shaft of a Land Rover providing a measure of distance at 100 mm intervals. This strobe controlled an analogue chart meter movement and it was also used to trigger data from the digital magnetometer frequency counter to the input of a Z80 micro controller in a data acquisition system developed by Sonotek in Canada. The Sonotek could read data acquisition programs from cassette tapes and it could write magnetic measurement data triggered at programmable fixed distance increments along traverse. Data tapes from the Sonotek were initially downloaded via cable to a mainframe computer at the University, but by 1984 a field portable PC was used.

 

Many thousands of survey km of magnetic data were acquired with this vehicle-borne system. For some applications where heading errors of up to 5 nT could be tolerated, the magnetic sensor was mounted on a 5 m wooden stinger behind the Land Rover. With this system, magnetic data could be acquired at 1 m intervals while traversing at 40 kph. Alternatively, a second operator could hand carry the sensor 30 m behind the vehicle thereby eliminating heading errors.

Absolute Total Field measurement.

Resolution: 0.1 nT @ 10 Hz.

Serial Number: 1

Year of manufacture: 1978

Origin: Geophysical Research Institute. Armidale, Australia