Deformation Type Thermometers Deformation thermometers use a coil made from two different kinds of metal. These metals expand and contract at different rates when heated. Depending upon which metal expands or contracts the most, the amount of expansion is measured and temperature can be read. Deformation thermometers are used in thermostats in houses and other buildings. They are also used in thermographs.
Thermographs are automatic temperature recording instruments.
The record on paper of temperature changes as recorded by a thermograph is called a thermogram. Other Thermometers Other kinds of thermometers include electrical thermometers, such as thermocouples, and resistance thermometers. All of these use electricity to measure temperature. A change in the air temperature causes a change in the electrical properties, like the electrical current generated or the electrical resistance. These types of thermometers are very accurate and respond rapidly to temperature changes.