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  Surveying Instrument Collection 


Tellurometer, South Africa


CA 1000

Serial Number

6250E ('Master' instrument)


Length 305 mm, Width 145 mm, Height 76 mm


Tellurometer CA 1000Tellurometer CA 1000


This Tellurometer CA 1000 is an electronic microwave distance measuring system capable of measuring distances from approximately 50 m to 30 km.

The complete system comprises of two instruments, namely the "Master" (S/N 6250E) and the "Remote" (S/N 6249E). Both are tripod mounted at each end of the line to be measured. The slope distance is obtained from readings taken by the operator of the Master instrument only. The two images shown above are separate views of the "Remote" unit. The master unit has an additional read-out switch and bezel to the right of the large dial. Both units radiate an X-band microwave carrier tuneable between 10.10 and 10.45 GHz which is frequency modulated in the 19 to 25 MHz range. The Remote unit receives the transmission and re-transmits it to the Master, which measures the phase difference between the transmitted and received signals.

The size, weight and power consumption of the CA 1000 has been kept to a minimum due to the use of miniature, solid-state components in the design. An optional battery tray can be mounted integrally with the instrument, providing power for about 200 measurements between charges. The operating procedure of this instrument has been made as simple as possible since there is no necessity, except under abnormal circumstances, for any tuning to be carried out by the Remote operator, as automatic frequency tracking is employed.

An interesting and highly efficient feature of this Tellurometer is that it incorporates a duplex speech facility, allowing radio communication between the two instruments during measurements, and thus eliminating the necessity for "walkie-talkies" or field telephones. Also, there is no warm-up period required, since the quartz-oscillator inside the instrument is largely independent of the temperature, and therefore does not need to be thermostat controlled.

The unusually shaped, four-sided horn antenna attached to the end of the distance meter, on the opposite side of the control panel, is the standard range (10 km) microwave antenna, which is used to project the microwaves from one instrument to the other. There is also a long range (30 km) horn antenna available with the instrument.

The probable error of a single determination of distance is less than 1.5 cm, and the scale error due to the uncertainty of the atmospheric refractive index determination and crystal frequency drift is usually less than 5 ppm. The instrument requires a 12 Volt dc power supply and the current consumption of the distance meter is 0.38 A.

History & comments

The Tellurometer was invented by Dr. T. L. Wadley, of the South African National Institute for Telecommunications Research. The first instrument, the MRA 1 was introduced in 1957. The CA1000 instrument was purchased by the then School of Surveying, UNSW, in the 1970's.


A tough plastic case


Good condition, well maintained

  • The 'Remote' unit is also available in the collection (see 0409)
  • Weight of instrument is 1.7 kg
  • Weight of battery tray with batteries is 2 kg.
  • Catalogued by T. Ko
  • Updated by F. Pall


Manufactured in 1970 (approx). Catalogued in 2000.

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