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Telemetric Magnetometer, TM-1

Telemetric Magnetometer, TM-1

Geophysical Research Institute. Armidale, Australia

1979

Method: Magnetics

Description

The success of the vehicle-borne magnetometer system was such that the vehicle undertook harsh treatment when required to survey straight lines through un-cleared, rough terrain. A hand-held option was desired. The Telemetric Magnetometer was conceived as a means of hand carrying the Cs sensor, magnetometer and odometer and to use a CB radio link to have this data logged in the vehicle-borne data acquisition system. An odometer was built which now deployed a “lost thread” system using bio-degradable cotton thread rather than a re-useable string as was the case with the first archaeological odometer. A digital frequency counter was built as an Honours Degree project by Stephen Lee under John Stanley’s supervision and the digital data encoded using frequency shift keying (FSK) was transmitted via CB radio. The TM-1 as it was called was a great concept so long as the radio link had integrity!

In late 1979 Sony released their first “Sony Walkman”, a portable, robust little stereo cassette recorder. A Sony Walkman soon replaced the troublesome CB radio. The position referenced, FSK coded magnetic data were now recorded on one track of the cassette while voice comments were recorded on the other. This facility enabled positioned geological observations to be simultaneously recorded. The Walkman tapes then had to be replayed in real time, for logging on the vehicle-borne data acquisition system prior to downloading to mainframe or PC.

The TM-1 was probably the first portable magnetometer with inbuilt memory. It certainly was the first with the capability to automatically record position with each magnetic measurement and to do so in sub-m intervals at traverse speeds faster than the operator could walk.

Absolute Total Field measurement.

Resolution: 0.1 nT @ 5 Hz.

Serial Number: 1

Year of manufacture: 1979

Origin: Geophysical Research Institute. Armidale, Australia

Weight: Sensor; 1.9 kg, Controller; 6 kg, Battery pack; 6 kg