Data Acquisition | Thermocouples |
| Thursday, 14 October 2004 | |
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Principle: When you have two dissimilar wires twisted together and if temperature end T1 is different that of T2 then current will flow through the wires. This effect was discovered by T.J. Seebeck and is referred to as the Seebeck Effect. Thermocouples do not measure a temperature but rather they measure a Temperature Difference.  The voltage potential generated also increases proportional to the difference in the two temperatures.   That is if a multimeter were connected across the wire ends,then we could multiply the voltage by a constant and get the temperature difference between T1 and T2. This constant we use is called the Seebeck coefficient and is based on the type of metals used for the wires. Let K be the Seebeck Coefficient Then V= K * [T2-T1] Example : Assume a K type of thermocouple where the two metals are Chromega (yellow) and Alomega (red), for these two metals the Seebeck coefficient is about 51uV/°C. Consider T1 is at 10°C and T2 is at 40°C. Then from the above formula: V=51 * [T2-T1] V=51 * [40-10] V=1530uV i.e 1.5mV |
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