Electronic Thermometer Circuit

A number of measurement circuits have appeared on this website. The project posted here is of Electronic Thermometer Circuit using op-amp 741. This circuit is suitable to measure temperature from 0⁰C to 50⁰C using a linear scale am-meter. The range can be extended up to 100⁰C using 100 microamperes.

Circuit Description of Electronic Thermometer Circuit using 741 IC

The circuit is self-explanatory for the experienced hobbyist and performs its task with a minimum number of components. The operational amplifier is used in compactor mode. The diodes D₁ and D₂ are used to sense temperature variation while op-amp is used to compare. Capacitor C₁ provides noise filtering.

Check out other Electronics Thermometer and Temperature related circuits posted in bestengineeringprojects.com

1. Electronics Thermometer Using Op-amp 741 IC
2. Electronic Room Thermometer Using Op-amp 741
3. PIC16F73 Based Temperature Indicator and Controller
4. Dynamic Temperature Indicator and Controller Using Ardunio

PARTS LIST OF ELECTRONIC THERMOMETER CIRCUIT USING OP-AMP 741

Resistor (all ¼-watt, ± 5% Carbon)

R1 = 8.2 KΩ R2 = 220 KΩ R3 = 5.6 KΩ R4 = 560 KΩ R5 = 18 KΩ VR1 = 4.7 KΩ VR2 = 1 MΩ

Capacitors

C1 = 1 µF, 10V (Electrolytic Capacitor) C2 = 150 pF (Ceramic Disc) C3, C4 = 100 KpF (Ceramic Disc)

Semiconductors

D1, D2 = 1N4148 (silicon switching signal diode) IC1 = 741 (General Purpose Operational Amplifier IC) IC2 = 7805 (5 Volt fixed series voltage regulator)

Miscellaneous

M1 = 50 µA SW1 = ON/OFF Switch B1 = 9V,PP3 Battery