A low cost tellurometer

Master Thesis


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University of Cape Town

This thesis describes the development of a low-cost microwave electronic distance measurement instrument using the Tellurometer phase-measurement principle. In a simplified form the instrument can be configured as a full-duplex 9 600 Baud datalink. The Tellurometer was invented in 1957 by the late Dr. Trevor Wadley of the National Institute of Telecommunications Research. Since then there has been a continuous development of Tellurometers that are used world-wide in the surveying profession. Sophisticated instruments are now available, but this development has been accompanied by increased costs and complexity. There is a growing need in underdeveloped countries for a simple low-cost microwave Tellurometer with good performance and maintainability. These countries survey with low budgets and cannot afford expensive equipment and do not necessarily require all the features and performance of today's instruments. To meet this need it has been the objective of this work to develop a Tellurometer with a range of 1O m to 15 km, with an accuracy in the order of 3 cm, and to keep the materials cost to within R700 per instrument. This has been reached by reducing circuit complexity, current consumption, and cost to a minimum, without compromising the required performance. Only essential features have been included, except where their inclusion has not compromised the cost. The use of a single -chip microprocessor, a simple narrow-band pattern-synthesiser, a low-cost microwave source, low-power technology and a very simple mechanical arrangement has resulted in a cheap simple instrument. Built-in test features of the software allow sophisticated maintenance with a minimum of test equipment.

Bibliography: leaves 94-96.