FAQ: What’s the Difference Between RTDs and Thermocouples?

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TEMPERATURE SENSORS
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RTD
THERMOCOUPLE

When choosing a temperature sensor for your industrial, laboratory, or process control application, the two most common technologies are RTDs (Resistance Temperature Detectors) and thermocouples. Each has its own strengths, limitations, and ideal use cases. Below, we break down the key differences to help you make an informed decision.

What is an RTD?

An RTD (Resistance Temperature Detector) is a temperature sensor that works by correlating the resistance of the sensor element with temperature. As temperature increases, the resistance of the metal (commonly platinum) increases in a predictable way.

What is a Thermocouple?

A thermocouple is a temperature sensor made from two dissimilar metals joined at one end. It works on the principle of the Seebeck effect, generating a voltage that corresponds to temperature differences between the junction and the opposite ends (called the reference or cold junction).

How do RTDs and Thermocouples Compare?

Feature

RTD

Thermocouple

Temperature Range

-200°C to ~600°C (up to 850°C in some cases)

-200°C to 1800°C (varies by type)

Accuracy

High (±0.1°C to ±0.5°C)

Moderate (±1°C to ±2°C typically)

Stability

Excellent long-term stability

Can drift over time, especially at high temps

Response Time

Slower than thermocouples

Fast response time

Durability

More delicate

Rugged, suitable for harsh environments

Signal Output

Resistance (requires bridge circuit)

Voltage (millivolts)

Cost

Generally more expensive

Generally less expensive

Wiring Requirements

2-, 3-, or 4-wire configurations

Simple 2-wire setup

Which Sensor would be recommended for My Application?

  • Choose an RTD if you need:
    • High accuracy and repeatability
    • Stable performance over time
    • Moderate temperature ranges
    • Laboratory, HVAC, or process control applications
       
  • Choose a Thermocouple if you need:
     
    • A wide temperature range (especially high temperatures)
    • Fast response times
    • Rugged design for industrial, automotive, or aerospace use
    • Cost-effective sensing in harsh environments

Can RTDs and Thermocouples be Interchanged?

Not directly. They operate on completely different principles and require different signal conditioning and wiring. 

Which is More Common in Industrial Applications?

Thermocouples are widely used in industrial applications due to their durability, simplicity, and ability to withstand extreme conditions. RTDs are more common in applications where precision and long-term stability are critical.

Still not sure which sensor is right for your application? Contact us today to speak with an experienced application engineer. We’ll help you choose the best solution for your temperature measurement needs.