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Instrumentation Reference Book, 4th Edition by Walt Boyes

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21.5. Measurement Techniques: Thermocouples

21.5.1. Thermoelectric Effects

If an electrical circuit consists of entirely metallic conductors and all parts of the circuit are at the same temperature, there will be no electromotive force in the circuit and therefore no current flows. However, if the circuit consists of more than one metal and if junctions between two metals are at different temperatures, there will be an EMF in the circuit and a current will flow. Figure 21.24 illustrates this effect. The EMF that is generated is called a thermoelectric EMF and the heated junction is a thermocouple.
B9780750683081000218/f21-24.jpg is missing
FIGURE 21.24.
Basic thermocouple circuit.

21.5.1.1. ...

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