| Platinum Resistance Thermometer | Thermocouple | Thermistor |
|---|---|---|---|
Sensor | Platinum-wire wound or flat-film resistor | Thermo-element, two dissimilar metals/ alloys | Ceramic (metal oxides) |
Accuracy (typical values) | 0.1 to 1.0°C | 0.5 to 5.0°C | 0.1 to 1.5°C |
Long term Stability | Excellent | Variable, Prone to ageing | Good |
Temperature range | -200 to 650°C | -200 to 1750°C | -100 to 300°C |
Thermal response | Wirewound – slow Film – faster 1-50 secs typical | Sheathed – slow Exposed tip – fast 0.1 to 10 secs typical | generally fast 0.05 to 2.5 secs typical |
Excitation | Constant current required | None | None |
Characteristic | PTC resistance | Thermovoltage | NTC resistance (some are PTC) |
Linearity | Fairly linear | Most types | Exponential |
Lead resistance effect | 3 & 4 wire – low | Short cable runs satisfactory | Low |
Electrical “pick-up” | Rarely | susceptible | Not susceptible |
Interface | Bridge 2,3 or 4 wire | Potentiometric input. Cold junction compensation required | 2 wire resistance |
Vibration effects/ | wirewound – not suitable Film – good | Mineral insulated types suitable | Suitable |
Output/ characteristic | approx. 0.4 W/°C | From 10µV/°C to 40µV/°C depending on type | -4% / °C |
Extension Leads | Copper | Compensating cable | Copper |
Cost | Wirewound – more expensive Film – cheaper | Relatively low cost | Inexpensive to moderate |
Comments and values shown in this chart are generalised and nominal. They are not intended to be definitive but are stated for general guidance.
The information given shows average application experience, but some of the considerations can be modified by special design or selection.
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