How Does a Dial Thermometer Work?
A dial thermometer is a type of thermometer that has a dial with a needle attached to it. The dial gives the thermometer's temperature reading. A dial thermometer is most often found in the kitchen; candy and meat thermometers are examples of the thermometer that is routinely available in dial form. Generally, a dial thermometer is used in situations where the thermometer would be inserted into an object and left there.
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Construction
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The dial thermometer is made up of very few parts. At the base of the thermometer, there is generally a metal stem that tapers into a probe shape on the bottom. Encased in the stem and extending up into the dial is a bimetallic strip. The bimetallic strip is connected to a spring in the dial. The spring is connected to and controls the needle in the dial.
Function
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When a dial thermometer is inserted into an object, the heat from the item penetrates the metal probe and warms the bimetallic strip. As the bimetallic strip heats, it bends at the top. This action puts pressure on the spring that is connected to the needle in the dial. As the strip grows hotter, it pushes harder on the spring. The spring, in turn, applies more pressure to the needle, forcing it farther over on the dial. When the dial thermometer is removed from the hot object, the bimetallic strip cools and releases the pressure on the spring.
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References
- Photo Credit Maria Li
