The thermocouple and thermistor both are sensing device for temperature measurement and control. Both resistance sensors but they have different working principle.
A thermocouple has two main wires that are welded into a junction. They are used because they can handle extreme temperatures. Versions that are built with precious metal junctions can withstand heats as high as 1800°C. Construction of a thermocouple system will cost more than a thermistor while providing less sensitivity and stability .
Thermistors use metal oxide beads that are encapsulated in either epoxy or glass. Typically, a thermistor will show large NTC. Depending on construction, thermistor prices and performances vary, but the device does come with standard benefits. Thermistors are highly sensitive and can be made small for sensing in small space.
Video Source By – Learning Engineering
The thermocouple is a type of device used for measuring the temperature.
Thermistor is the thermal resistor whose resistance changes with the temperature.
The thermocouples are made from metal or alloys of metals such as Copper, iron, chromium and platinum etc.
The thermistor is made by the semiconductor or oxides of magnesium, nickel or cobalt.
This is the symbol of thermocouple.
This is the symbol of thermistor.
The thermocouple has high accuracy.
The thermistor has very low accuracy.
The temperature measuring ranges of the thermocouple is -200°C to 1250°C.
The temperature measuring ranges of the thermistor is -50°C to 250°C.
In thermocouples, the variation in temperature is determined by the voltage induces at their junction.
The resistance of the thermistor changes when their surrounding temperature varies.
The thermocouple is expensive as compared to the thermistor.
The thermistor is Cheap.