In many heating systems and installations in everyday life and in production, a bimetallic thermometer is used, showing the change in temperature in a gaseous or liquid medium. This is a versatile device. It can be installed both indoors and outdoors. It is used in nuclear power plants, refineries, military ships, etc.
The bimetallic thermometer works on the basis of the following physical law: "Different metals expand or contract differently when the temperature of their environment changes." The sensitive element of the thermometer is a bimetallic spring (or plate) consisting of two different metals pressed against each other. Since they have different coefficients of expansion, they deform when the temperature of the medium rises or falls. The deformation of metals causes the thermometer needle to spin and show the temperature value on the scale.
The bimetal thermometer consists of a chrome-plated steel body, sensitive bimetallican element (springs or plates) enclosed in a brass bulb, a dial and a kinematic mechanism with an arrow. The dial and hand are covered with glass. A conventional thermometer can show temperatures ranging from -70°C to +600°C.
All bimetallic thermometers, depending on the fastening of the axis of the dial, are divided into two groups: basic and radial. The axis of the dial of an axial bimetallic thermometer is parallel to the axis of the bulb. A radial bimetallic thermometer differs from an axial one in that its axis is located at an angle of 90° to the bulb axis.
You can also classify the types of bimetallic thermometers according to the purpose of the device, at the place of its work. Depending on the purpose, thermometers are tube and needle. A bimetallic pipe thermometer measures the temperature of a pipe in a heating system from its surface. Needle bimetal thermometers measure temperature using a special probe-needle immersed in the medium.
Depending on the place of use, the devices are divided into household and industrial bimetallic thermometers. The temperature measurement range of household appliances is much smaller than that of industrial bimetallic thermometers. In the manufacture of household options, the conditions in which they have to work are taken into account.
Industrial bimetal thermometers are manufactured both with highly specialized capabilities and with universal ones. They can operate in any phase state andover a very wide temperature range.
The bimetallic thermometer is an excellent alternative to liquid. Its disadvantages are only that it is more expensive to manufacture and it takes longer to measure the temperature.
When purchasing a bimetallic thermometer, you need to pay attention to whether the device has a certificate of conformity and a passport. When working with the device, it is necessary to observe the temperature range indicated in the thermometer passport.
