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Choosing Between Thermocouples and RTDs
Selecting the right temperature sensor depends on several factors: required temperature range, response speed, accuracy, environmental conditions, and of course — cost.
| Feature | Thermocouples | RTDs |
|---|---|---|
| Temperature Range | Up to 2,500°C | Typically -200°C to +500°C |
| Accuracy | Moderate | High |
| Stability (Long Term) | Lower (drift over time) | Excellent |
| Response Time | Fast (tip-sensitive) | Slower (stem-sensitive) |
| Size and Ruggedness | Small, very rugged | Larger, less rugged (depends on design) |
| Signal Output | Low voltage (µV) | Higher (mV) |
| Cabling | Requires special extension wire | Standard copper wire |
| Cost | Low | 2–3x higher (but falling with modern designs) |
When to Use Thermocouples
- Best for: High temperatures, fast-changing processes, harsh or corrosive environments
- Advantages: Simple, robust, inexpensive, and responsive
- Limitations: Less accurate, non-linear signal, requires reference junctions and careful installation
-
Design Considerations:
- Life expectancy drops rapidly above 500°C unless larger wires and protective sheaths are used
- Noble metal types offer extended ranges but are sensitive to contamination
- Refractory types are suited to extreme environments but can drift under high-temperature stress
When to Use RTDs
- Best for: Laboratory, industrial, and HVAC systems where accuracy and stability are key
- Advantages: Highly accurate, stable over time, linear output, easy signal conditioning
- Limitations: Slower response, more fragile, sensitive to vibration and radiation
-
Design Considerations:
- Use platinum RTDs for broad compatibility and precision
- Thin-film RTDs are closing the gap on thermocouples for cost and ruggedness
- Ensure proper shielding in high-radiation or vibration-heavy environments
Summary
In short:
- Thermocouples win on cost, ruggedness, and range
- RTDs win on accuracy, repeatability, and ease of measurement
For general industrial use, thermocouples remain the go-to. For precision applications or long-term monitoring, RTDs are the better choice.
Note: The information in this guide is provided for general informational and educational purposes only. While we aim for accuracy, all data, examples, and recommendations are provided “as is” without warranty of any kind. Standards, specifications, and best practices may change over time, so always confirm current requirements before use.
Need help or have a question? We’re here to assist — feel free to contact us.
Further Reading
RTD vs Thermocouple – Choosing the Right Sensor
Explore the features and characteristics of thermocouples and RTDs
RTD Output Tables
View Resistance versus Temperature tables for all Pt100 sensors.
What are the RTD colour codes?
Explore RTD colour codes and wiring configurations.