This is a thermometer with 3 1/2 digit LCD display for measuring the ambient temperature. The sensor is an integrated circuit S-8100BF, which is usually used for temperature compensation. This device includes also a 3 1/2 digit convertor ICL7106 and a high precision voltage regulator LM723. The unit was ready for the first use in 1996. Later in 1999, I made some modifications to allow a better temperature calibration, using an integrated circuit LM723 as voltage reference.

In 2012 I have dismantle this thermometer to use the same components and printed circuit board for a voltmeter.

Main sensor features are:
-linear output voltage: -8.1 mV / °C
-temperature range: from -40°C to 100 °C
-linearity: ±1% (-20°C to 80 °C)
-repeatability: ±0.3 °C
(for complete list of specifications, see [2])

Thermometer specification:
- measuring domain: from 0°C to 50°C (estimated)
- resolution: 0.1°C
- accuracy (estimated): ± 1°C
- powered from mains socket: 230 VAC
- Schematic diagram

The main advantage of this project is the calibration without having a temperature reference, using only the voltage references provided by LM723. The two potentiometers will be adjusted until the two reference voltages ZERO and SCALE indicated in the schematic diagram are obtained.

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Reference links:
[1] - 3 1/2 digit A/D converter ICL7106/7107
[2] - CMOS temperature compensation IC: S-8100BF
[3] - High precision voltage regulator: LM723