Several different types of mechanical thermometers are commonly used:
1. The Bimetal Thermometer
Two different metals with different coefficients of thermal expansion are bonded together. As a change in temperature occurs the unequal expansion to the two metals will cause the bimetal strip to curl. If one end of the metal strip is fixed than the other end will be displaced in response to temperature changes. Bimetal strips can be fabricated into coils, spirals and disks.
2. Liquid Expansion Thermometer
The volumetric expansion of liquids and solids can be used for temperature measurement. Mercury and alcohol filled thermometers work under this principle.
3. Gas Thermometer
A gas filled thermometer operating under the principles of the ideal gas law (PV = nRT) can be used for temperature measurement. If pressure is held constant the change in gas volume can be used to indicate temperature.
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Support for the development of this module was provided by the National Science Foundation and The Cooper Union for the Advancement of Science and Art.
Please send questions or comments to Professor Ron Adrezin or Professor Daniel Raichel.