Choosing a
thermometer
Different types of thermometers are used in a wide range of applications and situations. Factors to be considered include size, accessibility and required temperature ranges.
| Type | Measured Property | Temperature Range | Features |
|
Liquid-in-glass thermometer |
Thermal expansion of the liquid | -100 ºC to 300 ºC | Can break! |
|
Electrical resistance thermometer
Platinum resistance
Standard Platinum Resistance (SPRT)
Industrial platinum resistance (IPRT, PT100s, RTD (resistance temperature detector)
Thermistor |
Electrical resistance |
-250 ºC to 600 ºC |
Very accurate
Laboratory use
Industrial use
Small probes, fast response, but limited temperature changes. |
|
Thermocouple thermometer |
Voltage generated by 2 wires made out of different metals |
-200 °C to 2000 °C |
Cheapest and most common |
|
Radiation thermometers |
Intensity of infrared (heat) radiation given out by an object |
-400 °C to 3000 °C |
No need to contact the object to measure its temperature |
Having chosen a thermometer, it is important to ensure that its readings are reliable. This means that:
- thermometer must comply with the relevant specification standards
- it must be used appropriately
- it must be calibrated before being put into service
- it must be repeatable within the temperature range of use
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