Length 330mm, Width 330mm, Height
508mm (yoke plus barrel)
This precision electro-optical Tellurometer Model MA100 is specifically
designed for short-range high-accuracy distance measurement. The
instrument can be used for precise traversing, constructional 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 kilometres or more with an instrumental
accuracy of a few millimetres. 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 kilometres.
The instrument makes use of phase comparison techniques to determine the
distance and 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 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 lining up on the aiming 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.
For distance measurement, under favourable atmospheric conditions, 1 km
can normally be measured using a triple prism reflector and 2 km
distances require 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 atmospheric refractive index determination
is usually less than ±2 ppm.
The instrument requires a 12V D.C. power supply and the average power
consumption of the distance meter is 15 W.
A tough plastic case
Total weight of instrument (without case) is 17.3 kg