| Comparative Points |
Resistance Thermometer or RTD |
Thermocouple |
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| Working Principle |
RTD directly measures the actual temperature of object, because electrical resistance is directly proportional to temperature. |
Thermocouple measures the temperature difference between hot junction and cold junction. |
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| Material used |
Metals like Copper, platinum, Nickel etc. |
Metals like Copper, Iron, Platinum, Rhodium or alloys like Constantan. |
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| Output reading |
Actual temperature of object. |
Temperature difference between temperature of cold junction and hot junction. |
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| Temperature range |
Low range of measurement from – 200°C to 1000°C. |
Wide range of measurement from – 200°C to 1600°C. |
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| Sensitivity |
RTD is more sensitive than thermocouple. |
Less sensitive due to very small emf output. |
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| Effect of change in atmospheric temperature |
No effect on accuracy of measurement. |
Affects accuracy of measurement. |
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| Response |
Better response. |
Comparatively slow response. |
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| Cost |
High cost. |
Moderate cost. |
