A thermometer is a device that measures temperature or a temperature gradient. A thermometer has two important elements :
- A temperature sensor (e.g. the bulb on a mercury-in-glass thermometer) in which some physical change occurs with temperature, and
- Some means of converting this physical change into a numerical value (e.g. the visible scale that is marked on a mercury-in-glass thermometer).
Details :
- There are various principles by which different thermometers operate. They include the thermal expansion of solids or liquids with temperature, or the change in pressure of a gas on heating or cooling. Radiation-type thermometers measure the infrared energy emitted by an object, allowing measurement of temperature without contact.
- Thermometers are widely used in industry to control and regulate processes, in the study of weather, in medicine, and scientific research.
- Some of the principles of the thermometer were known to Greek philosophers of two thousand years ago; by the 18th century, standardized scales allowed the readings of different thermometers inter-comparable.
