Tellurometer | Tellurometer In Surveying
This instrument was developed by TL under the auspices of the South African Council for Scientific and Industrial Research. Wadley.
There are two types of tellurometers. One gives the output of the delay line in terms of transit time and another the direct reading in meters.
It uses high-frequency radio waves. Two identical pieces of equipment is installed at the two stations that need the distance.
The master tool sets the code and the remote tool receives, monitors, and returns it to the master. However, The distance obtained is checked by reversing the roles of the master and the remote tellurometer. It could be used during the day and at night.
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However, A block diagram of the tellurometer system is shown in Fig. 2.48. The master set emits the microwaves at a frequency of 3 Mcps and is modulated by the pattern wave at a frequency of 10 Mcps.
Block diagram of tellurometer system:
The combined wave is reflected by the remote apparatus. The master tool then separates the sample wave to measure the phase delay. Four low frequencies A, B, C, D values of 10, 9.99, 9.90, 9.00 Mcps are used in the master station.
The corresponding delay values for each of these are measured in an oscilloscope cathode ray tube. The phase delay of B, C, and D is subtracted from A by turns.
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Moreover, The values of A are called good readings, while the values of B, C, and D are called coarse readings. The wavelength of a sample of 10 Mcps is approximately 30 m.
However, The oscilloscope scale is divided into 100 parts, each segment being 0.3 m and a two-way travel representation of 0.3 m radio waves, or about 0.15 m in line length.
Therefore, The four final readings of the A, A – B, A-C, and A – D are recorded in –9 millimicrons seconds (10 seconds) and are converted into distance reading by assuming the velocity of wave propagation as 299 792.5 km/s.