At the risk of repeating myself, temperature may well be the world’s most surveyed physical quantity. Several methods exist to measure temperature. In electronics the most common ways to do it are: 1. thermistor: a device whose resistance increases (positive temperature coefficient or PTC) or decreases (NTC) with temperature; 2. Resistance Temperature Detector (RTD): exploits the precisely known relationship between temperature and resistance of a material, typically a metal like platinum; 3. thermocouple: a junction of two different metals that produces a temperature-dependent voltage as a result of the thermoelectric (Seebeck) effect; 4. semiconductor-based sensors: the voltage across a diode or PN junction decreases by approximately 1 to 2 mV per degree Celsius; 5. infrared thermometer: infers temperature from thermal radiation. The last technique is often used to measure human body temperature by pointing a ‘temperature gun’ at the insides of an ear. Up to this point nothing new, you say, discreetly suppressing a yawn, but did you know that you can use the ear itself to determine the temperature?
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