Pt100 or thermocouple — which measuring principle fits?
The question is almost always decided by the temperature. Up to +600 °C the Pt100 is the more accurate and more stable solution; above that no platinum resistance element measures any more — then the thermocouple remains.
In between, response time, cable run and cost decide.
Up to +600 °C both principles overlap, above that only the thermocouple remains.
Comparison
| Resistance thermometer Pt100 / Pt1000 | Thermocouple | |
|---|---|---|
| Measuring range | −200…+600 °C | −200…+1,700 °C depending on type |
| Accuracy | higher; class AA up to 1/10 DIN B possible | lower; class 1 to 3 to DIN EN 60584 |
| Long-term stability | very good, wire-wound especially | drift as the thermocouple ages |
| Response time | longer | shorter, grounded from about 0.15 s |
| Cable | ordinary copper cable | thermocouple or compensating cable, type-matched |
| Reference junction | not needed | needed, otherwise systematic error |
| Vibration | thin-film good, wire-wound more sensitive | very robust |
| Cost | higher at small diameters | lower, type J and K especially |
Rules of thumb
- Up to +600 °C Pt100 — more accurate, more stable, easier to wire.
- Above +600 °C Thermocouple. Type K or N in furnace construction, type S, R or B for noble-metal applications from 1,200 °C.
- Rapid temperature changes speak for the thermocouple with a grounded measuring junction or for a thin mineral-insulated sensor.
- Long cable runs speak for the Pt100 — compensating cable over 30 m becomes expensive and error-prone.
- Many identical measuring points with a moderate accuracy requirement: thermocouple type J or K is the more economical solution.
The same form is usually available in both variants
Our thermowell thermometers come in pairs: WSK-2 as Pt100 and TSM-2 as thermocouple, WSK-3 and TSM-3, WEK-2G and TET-2G. Installation dimensions, connection head and thermowell are identical — so you can switch between the measuring principles without rebuilding the measuring point.
| Pt100 with thermowell | Thermowell thermometers Pt |
| Thermocouple with thermowell | Thermowell thermocouples |
| Pt100 as a mineral-insulated sensor | Mineral-insulated resistance thermometers |
| Thermocouple as a mineral-insulated sensor | Mineral-insulated thermocouples |
Borderline case at 500 to 700 °C?
Then a short conversation pays off: medium, cycles and the required uncertainty decide. We will tell you what we use at comparable measuring points.
Tolerance classes Pt100
Thermocouple types
All resistance thermometers
All thermocouples
Question about the design?
Tell us the medium, temperature and installation situation — you will have a proposal within one working day.