Electronic thermometers & their functional principles

Many thermometers today are electronic. Let’s see how different types of electronic thermometers are made and what are their working principles.

1 ) Most contain a tiny bead of a semiconducting material whose resistance varies with temperature. The bead is called a thermistor, or thermal resistor.

2 ) Others contain a tiny semiconducting diode. The voltage across this diode varies with temperature.

3 ) To measure very high temperatures, a wire made of the metal platinum is used because its resistance also varies with temperature, and platinum is not affected by high temperatures.

4 ) Another electronic thermometer uses two wires made of different materials that are welded together. Typically the wires are made of copper and a nickel-containing alloy. This kind of thermometer is called a thermocouple and is often used in gas furnaces or water heaters to make sure that the pilot flame is burning when the gas to the main burners is turned on.

Electronic thermometers & their functional principles
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