Sensores de alta temperatura
Comparison of Sensor Types
| Thermocouple | Platinum Resistance Thermometer | Thermistor |
Sensor | Thermoelement, two dissimilar metals/alloys
| Platinum-wire wound or flat-film resistor | Ceramic (metal oxides) |
Accuracy (typical values) | 0.5 to 5.0°C | 0.1 to 1.0°C | 0.1 to 1.5°C |
Long term Stability | Variable, Prone to ageing | Excellent | Good |
Temperature range | -200 to1750°C | -200 to 650°C | -100 to 300°C |
Thermal response | Sheathed – slow Exposed tip – fast 0.1 to 10 secs typical | Wirewound – slow Film – faster 1-50 secs typical | generally fast 0.05 to 2.5 secs typical |
Excitation | None | Constant current required | None |
Characteristic | Thermovoltage | PTC resistance | NTC resistance (some are PTC) |
Linearity | Most types non-linear | Fairly linear | Exponential |
Lead resistance effect | Short cable runs satisfactory | 3 & 4 wire – low. 2 wire – high | Low |
Electrical “pick-up” | susceptible | Rarely susceptible | Not susceptible |
Interface | Potentiometric input. Cold junction compensation required | Bridge 2,3 or 4 wire | 2 wire resistance |
Vibration effects/ shock | Mineral insulated types suitable | wirewound – not suitable. Film – good | Suitable |
Output/ characteristic | From 10µV/°C to to 40µV/°C depending on type | approx. 0.4 W/°C | -4% / °C |
Extension Leads | Compensating cable | Copper | Copper |
Cost | Relatively | Wirewound – more expensive Film – cheaper | Inexpensive |
Comments and values shown in this chart are generalised and nominal. They are not intended to be definitive but are stated for general guidance. |