Cost: Comparing to RTD, Thermocouple is lesser expensive.
Temperature Range: Extends to about 1150°C or higher. However, the thermocouple’s cryogenic range is somewhat less than that of the RTD.
Mounting cost: Lower than RTD
Ruggedness: For process environmental condition, high temperature, vibration, thermocouple are regarded highly.
Stability: Less than for the RTD. Estimated at 0.6◦C (1◦F) per year.
Calibration: Nonlinear over normal spans. Signal requires linearizing. Calibration can be changed by contamination.
Accuracy: Generally expected, after installation, ±4◦C (±7.2◦F), but there are exceptions. Thermocouple requires reference junction or special wires. The inaccuracy is due to two separate temperature measurements - the measuring junction and the cold or reference junction.
Accuracy: Accepted after installation ±0.5◦C. The platinum RTD, for example, is used to define the IPTS at the oxygen point (−182.97◦C) and the antimony point (+630.74◦C).
Repeatability: Within a few hundredths of a degree; can often be achieved with platinum RTDs. Less than 0.1% drift in 5 years.
Relatively narrow spans: Some versions may have spans as narrow as 5.6◦C (10◦F).
Substantial output voltage (1 to 6 volts): This is an advantage in that the output can be controlled by adjusting the current and the bridge design in the RTD signal conversion module. Because of a higher output voltage to the RTD and controlling of temperature signals is simpler. This permits more accurate measurements without requiring complex calculations for large spans
Compensation: Not required.
Size: Generally smaller than thermocouples
Cost: Higher than the thermocouple. RTDs do not require compensation, special lead-wires, and special signal conditioning for long runs.
Less rugged: For adverse process environments, including high temperature and vibration.
Lower temperature range: Limited to about 870◦C (1600◦F).
Self-heating errors: This may be a problem unless corrected in the transistor’s electronics.