How is temperature measured?
Temperature is measured by a thermometer. A thermometer is a device in which a property that changes with temperature is measured and used to indicate the value of the temperature
A thermometer has two important elements:
- A sensor which responds to temperature changes
- A means of converting the sensor response into values of temperature
Different types of thermometer:
In the modern world, mercury and spirit filled thermometers have largely given way to electrical devices.
The vast majority of contact temperature measurements use resistance thermometers or thermocouples. They can be used at very low or very high temperatures with good accuracy and the instrumentation can be automated
For measuring very hot, moving or distant objects infrared radiation thermometry avoids many of the problems of using a contact sensor, but has to take into account the radiative properties of the particular surface being measured and its environment.
NPL has made the most accurate thermometer ever which works by measuring the speed of sound in gas.
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