How to identify thermocouple and RTD?



How to identify whether temperature sensor is RTD or Thermocouple?

1.Lead Wires

RTD has two,three or four leads per sensing element
Thermocouple has two leads per junction
RTD typically have red,white,green or black leads
TC color match thermocouple type- red(common),yellow,purple,blue,white.

2.Resistance check

RTD will have about 109 ohms between leads at 20 deg C
Thermocouple lead resistance is typically less than 1 ohm

3.Continuity check

TC grounded junction has path from leads to case

4.Magnet test

RTD leads are not magnetic
TC type J has one iron lead which is highly magnetic