The difference of thermocouple and RTD

1. Measuring principle

The measuring principle of thermocouple is based on thermoelectric effect(Seebeck Effect), mainly type K,J,N,T,E,S,R

The measuring principle of RTD is based on the property that the resistance value of conductors or semiconductors change with temperature,mainly type PT100 and PT1000.

2. Structure

The structure of RTD usually consists of resistive element, connecting wire and sheath. The structure of thermocouple usually consists two metal wires of different materials by welding together.

3. Temperature ranges

Thermocouple measurement range is wide. Common thermocouple can be measured from -50 to 00℃. RTD can be measured from -200 to 650℃. The temperature zone measured by thermocouple is much wider than RTD.

4. Accuracy

The measuring accuracy for RTD is more specific than thermocouple’s.Since thermocouples have a high measurement range and good stability, they are often used for temperature measurement in high temperature environments and extreme conditions. Thermal resistors are more commonly used in normal and medium temperature ranges.

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