Electronic – Differences between thermistors and thermocouples

sensortemperaturethermistorthermocouple

As I understand it, both thermistors and thermocouples are temperature sensors. So what are the advantages/disadvantages of using one over the other to measure the temperature?
What are the specific applications for either of the sensors?

Best Answer

Thermocouples:

  • wide range of temperature sensing (Type T = -200-350°C; Type J = 95-760°C; Type K = 95-1260°C; other types go to even higher temperatures)
  • can be very accurate
  • sensing parameter = voltage generated by junctions at different temperatures
  • thermocouple voltage is relatively low (4.3mV for Type T thermocouple with one end at 0 C, other at 100 C, so that's 43uV/C tempco)
  • mostly linear

Thermistors:

  • more narrow range of sensing (Quality Z thermistors spec'd at -55 to +150 C)
  • sensing parameter = resistance
  • usually very nonlinear
  • NTC thermistors have a roughly exponential decrease in resistance with increasing temperature
  • good for sensing small changes in temperature (unless you are careful in your signal conditioning, it's hard to use a thermistor accurately and with high resolution over more than a 50 C range).
  • sensing circuit doesn't need amplification & is very simple (voltage divider with reference resistor tied to reference voltage usually is sufficient) – see my blog for more information about signal conditioning.
  • accuracy is usually hard to get better than 1°C without calibration
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