MSc Dissertation: Jonathan Ward


Adobe-PDF-downloadWard, Jonathan M. Design and Implementation of a Non-Contact Level Measurement Instrument. MSc Dissertation. Department of Electrical Engineering, University of Cape Town, 2010.



This dissertation describes the design and implementation of a microwave level measurement instrument for sensing the level of a substance inside a tank up to 10 m in height. A radar transceiver had to be designed to replace an acoustic sensor on an existing 4-20 mA loop powered ultrasonic instrument and had to be compatible with its on-board acoustic signal processing hardware. Specifications are developed for a pulsed radar architecture operating at 5.8 GHz with a bandwidth around 1 GHz and at a repetition frequency of 3.58 MHz. A Venier time stretching technique is used to perform the distance measurements by cross-correlating the transmit pulse train with a separate but similar reference pulse train operating at a slightly lower repetition frequency, setting up an output range profile with ultrasonic time interval measurement parameters. Demonstration hardware operating at 580 MHz with 100 MHz bandwidth and at a repetition frequency of 3.58 MHz is designed and built. Short pulses (< 1 ns) with rise-times in the order of hundreds of picoseconds are generated and shaped into 12 ns RF pulses using bandpass filtering. Tests are performed to measure the time interval between the transmitted pulse and echo at several ranges, which show an overall accuracy of less than the required 2 cm can be achieved using the proposed system.



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