Temperature Sensors - Comparing Types

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Temperature Sensors - Comparing Types
Attribute	Thermocouple	RTD	Thermistor
Cost	Low	High	Low
Temperature Range	Very wide -350 ^oF +3200 ^oF	Wide -400 ^oF +1200 ^oF	Short to medium -100 ^oF +500 ^oF
Interchange ability	Good	Excellent	Poor to fair
Long-term Stability	Poor to fair	Good	Poor
Accuracy	Medium	High	Medium
Repeatability	Poor to fair	Excellent	Fair to good
Sensitivity (output)	Low	Medium	Very high
Response	Medium to fast	Medium	Medium to fast
Linearity	Fair	Good	Poor
Self Heating	No	Very low to low	High
Point (end) Sensitive	Excellent	Fair	Good
Lead Effect	High	Medium	Low
Size/Packaging	Small to large	Medium to small	Small to medium

A thermocouple has two dissimilar conductors forming electrical junctions at differing temperatures. The thermocouple produces a temperature-dependent voltage as a result of the thermoelectric effect and can be interpreted as a temperature measurement.
A RTD - Resistance Thermometer Detector - are made of a length of fine wire wrapped around a ceramic or glass core. The RTD wire is of pure material - typically platinum, nickel, or copper - with an accurate resistance/temperature relationship. The electrical resistance provides an indication of the temperature.
A thermistor is a type of resistor made of ceramic or polymer materials. The resistance is - like the RTD - dependent on temperature.