PRECISION THERMOMETRIC SYSTEM USING RADIO TELEMETRY WITH COMPUTER INTERFACING

Abstract

A precise temperature monitoring system in the range 50-1350uC using Radio Telemetry as a means of signal transmission has been designed and constructed. It consists of a sensitive thermocouple amplifier with active cold junction compensation. To enable FM Telemetry, the output voltage was linearly converted into pulses of proportional frequency and then pulse modulated for transmission as radio signals. The signal is then demodulated by a YHF receiver and subsequently processed. The system, which consists of two modules works as a general-purpose temperature-monitoring device with an accuracy of ± 1-c. For the purpose of data logging the measured temperature, a precise computer-interfacing adapter was also designed and constructed. It includes a TC71 09 12-bit AID converter and two octal D-type latches which provide the handshaking and necessary multiplexing action required to input 12-bit through the 8-bit data port available for input on the parallel port of the computer. The unit is designed to enable its use as a general-purpose device for other inputs other than a thermocouple amplifier output. The software for the control, data processing and presentation of output (result of computation) on a graphical screen of the VDU of the computer was written in QBasic and Visual Basic, the codes of which can easily be adapted to suit the users purpose.