Comparison

RTD vs Thermocouple: Which Temperature Sensor Fits?

RTDs are accurate and stable. Thermocouples reach very high temperatures and tolerate vibration. Compare range, accuracy, response and wiring.

Controls & Instrumentation · Last reviewed October 17, 2026

Short answer: choose an RTD for accurate, stable measurement up to about 600 °C, such as in HVAC, food and process work. Choose a thermocouple for very high temperatures, fast response, rugged or vibrating installations and low cost.

	RTD (for example Pt100)	Thermocouple (for example type K)
Temperature range	About −200 to 600 °C for common types	About −200 to over 1,200 °C for type K, and higher for other types
Accuracy	Better. Class A is about ±(0.15 + 0.002 × t) °C, which is ±0.35 °C at 100 °C	Typical standard limits are about ±1.5 to ±2.2 °C or a fraction of a percent of the reading, which is looser than an RTD
Stability and drift	Very stable over time	Can drift as the wires age, especially at high temperature
Response time	Slower, with a larger element	Fast, especially with a small junction
Output	Resistance, about 0.385 Ω/°C for Pt100, which needs an excitation current	A small voltage, about 0.04 mV/°C for type K, which needs cold-junction compensation
Wiring	2, 3 or 4 wires, with copper cable. Lead resistance matters for 2-wire	Thermocouple extension wire of the right type, with correct polarity
Vibration and shock	More fragile element	Rugged
Cost	Higher sensor cost	Lower sensor cost, though the extension wire can cost more
Typical uses	HVAC, pharmaceutical, food, laboratory, process control	Furnaces, exhausts, kilns, engines and high-temperature processes

How to choose

Check the temperature range, including upsets. Above about 600 °C the choice is usually a thermocouple.
Decide how accurate and stable the reading must be. A control or billing measurement favors an RTD.
Check the response time needed, and the effect of any thermowell.
Look at vibration, shock and the installation conditions.
Check the input module: it must match the sensor type and wiring. Plan wiring and the cost of cable.

Common mistakes

Using a 2-wire RTD with long leads, which adds an offset (3 Ω of lead resistance is about 7.8 °C on a Pt100).
Using ordinary copper wire for a thermocouple.
Configuring the input for the wrong sensor type.
Choosing an RTD for a very hot, vibrating location where it will fail.

Related tools and labs

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Questions

Can I replace a thermocouple with an RTD?

Only if the range allows it and the input module is changed to suit. The wiring and the transmitter or input type must match.

Why does a thermocouple need cold-junction compensation?

The voltage depends on the difference between the hot and the cold junctions, so the instrument has to measure the terminal temperature and correct for it.

Educational material. Examples use simplified, hypothetical inputs and are not a design, a construction document or professional engineering advice. Confirm requirements with the codes and standards adopted where the work is built and with a licensed engineer.

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