Description

One of a pair of Tellurometer MRA3 distance measurers used by the donor in the early 1970’s as part of the British Antarctic Survey (BAS). The device is contained in a self-sealing and rain-proof metal case with a leather carrying handle. The control panel is accessed by removing the case’s back cover. A fitted framed haversack is used to transport the instrument. (See partner tellurometer 2025-005-2).

The tellurometer is a transistor instrument that is used for the accurate measurement of distances in surveying. To carry out a measurement, an instrument is positioned at each end of a line; by means of a switch, either instrument can be set to act as a Master unit and the other as a Remote unit. The instruments are capable of consistently measuring distances in excess of 50 (fifty) km. Under favourable conditions and subject to zero-error calibration, the overall measuring error is ± 1.5 cm ± 3 parts per million of the length being measured. For accurate results, it is necessary to take readings on a number of successive carrier frequencies in order to average out the effects of ground reflections, which cause the indicated readings to differ from the true readings. For long-range measurements, it is necessary to take accurate readings of atmospheric pressure, temperature, and humidity in order to calculate the refractive index of the atmosphere. For short-range measurements (below about 200 metres), calculation of the refractive index of the atmosphere is unnecessary.

The device is accompanied by:

• Canvas fitted framed haversack
• Tellurometer MRA3 Headset Assembly
• Tellurometer MRA3 Battery Cable
• Tellurometer Service Record
• BAS Log Book for Tellurometer MRA3 Serial No 2356
• Spare fuses (4 No)

The donor, Jonathan Walton, writes:

Ex British Antarctic Survey – used by myself in the early 1970’s. Last time I tried them, after they had been serviced, they worked. MRA3 is the rugged (militarised) version of the earlier Tellurometer 101. Tellurometer, a South African firm, made the first ever Electromagnetic Distance measuring kit which came out in about 1960. Enormous bulky machines but they revolutionised surveying. They were refined – the MRA3 was probably the most successful of all the models and relatively compact – would work from -40C to +40C (and I checked this out, at -45C they wouldn’t work! – these exact machines). They were serviced after BAS got rid of them … and I had them working – once.

The donation is also accompanied by:

• Instruction Manual for the Operation and Maintenance of the Tellurometer MRA 3 MK II (December 1967)
• Tellurometer Microwave System of Distance Measurement / MRA3 Dial Read-Out Operating Instructions (TI/T3/H) (x2)
• “‘Micro-Distancer’ Model MRA3” Field Record pad
• “CA1000 Field Record” pad