Electronic Thermometer Using ICL7106

This is a very simple electronic thermometer with LCD display. The ICL7106 Integrated circuit contain all the active circuitry for a 3 1/2 digit panel meter (DPM) in a single chip. It was designed to interface directly to a liquid crystal display (LCD).

Electronic Thermometer Using ICL7106 Circuit Diagram

ICL7106 Circuit Diagram

The potential difference across a silicon diode is dependent on its temperature and current through it. Its temperature coefficient is negative, that is, the voltage falls with increasing temperature. This fall is approximately linear and is typically -2.2mV/oC.

The temperature meter measures the potential difference across the diode after an offset voltage which is available from pins 1 and 32 of the 7106 has been added. The two 100K 10-turn trimpots are used to calibrate the sensor at two known temperatures.

The calibration is easily done using water with ice in it to calibrate zero degrees Centigrade and putting the sensor in a jet of steam from a boiling water kettle to calibrate for 100 C degrees .
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