0408
   PRECISION DISTANCE METER  
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  Surveying Instrument Collection 

Maker

Tellurometer, South Africa

Model

MA 100

Serial Number

359

Dimensions

Length 330 mm, Width 330 mm, Height 508 mm (yoke plus barrel)

Image

Tellurometer MA 100

Description

This precision electro-optical Tellurometer Model MA 100 is specifically designed for short-range high-accuracy distance measurement. The instrument can be used for precise traversing, construction surveys, mining surveys, cadastral surveys, control for aerial photography and valuation surveys in urban and semi-urban areas. It is capable of measuring distances up to 3 km or more with an instrumental accuracy of a few millimetres. The meteorological errors will not contribute more than 2 parts per million of the range being measured, hence the overall accuracy can be expected to vary from a few millimetres at short range to about 1 cm at 3 km.

The instrument makes use of phase comparison techniques to determine the distance. The actual phase measurement is performed digitally using a pulse counting system and a clock oscillator. A measuring frequency of about 75 MHz is modulated on to a light source (Gallium Arsenide diode) emitting at a near infra-red with wavelengths of 0.92 micrometres and the returned light is detected by a photo diode. 

The instrument consists of a magnesium alloy barrel containing the optics, and is mounted on a cast alloy yoke above the instrument body which contains the electronic circuitry, control panel and readout. The optical barrel is completely sealed and has a cartridge of silica gel which provides further protection against possible ingress of moisture. Vertical clamp and tangent screws are mounted in the yoke while the horizontal clamp and tangent screws are an integral part of the azimuth mount assembly below the instrument body. The instrument is carried by means of a heavy duty leather strap which is slung across the yoke.

A telescope, used for pointing to a target, is usually mounted at eyelevel on top of the optical barrel, however, it is unfortunately missing from the collection. A data output socket on the front panel provides range information in binary-coded-decimal form for direct input into a tape punch or other recording device.

Under favourable atmospheric conditions, 1 km can normally be measured using a triple prism reflector and 2 km with four triple prism reflectors. The standard deviation of a single determination of distance due to instrumental errors is 1.5 mm and the scale error due to the uncertainty of the atmospheric refractive index determination is usually less than 2 ppm.

The instrument requires a 12 V dc power supply. The average power consumption of the distance meter is 15 W. 

History & comments

There is no historical information available.

Conservation

A tough plastic case

Condition

Good, however the pointing telescope is missing.

Remarks
  • Total weight of instrument (without case) is 17.3 kg
  • Catalogued by T. Ko
  • Updated by F. Pall

Dates

Manufactured in 1963 (approx). Catalogued in 2000.

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