Bimetallic electric contact thermometer
Structure and principle
Principle of bimetallic strip: The bimetallic electric contact thermometer is mainly based on the thermal expansion principle of bimetallic strip. A bimetallic sheet is composed of two metal sheets with different coefficients of thermal expansion tightly bonded together. When the temperature changes, due to the different degrees of thermal expansion of the two metals, bimetallic sheets will undergo bending deformation. For example, a bimetallic strip composed of copper and iron, when the temperature increases, the metal with a larger expansion coefficient (such as copper) elongates more, causing the bimetallic strip to bend towards the side of the metal with a smaller expansion coefficient (such as iron).
Electric contact part: It adds an electric contact device on the basis of the bimetallic sheet. When the bimetallic strip bends to a certain extent due to temperature changes, it will cause the electrical contacts to close or open, thereby achieving temperature control and signal output. Electric contacts are generally connected in control circuits. When the temperature reaches the set value, the operation status of the equipment is controlled through the action of the electric contacts, such as starting or stopping the heating equipment, issuing alarm signals, etc.
Application scenarios
Industrial temperature control: used in industrial production processes to control the temperature of various heating or cooling equipment. For example, in chemical production, precise control of the temperature inside the reaction vessel is necessary. When the temperature inside the reaction vessel reaches the upper limit temperature set by the bimetallic electric contact thermometer, the electric contact will activate, cutting off the heating source to prevent the reaction temperature from being too high; When the temperature drops to the lower limit temperature, the electrical contact will activate again, start the heating source, and maintain the reaction temperature within the appropriate range.
Temperature control of living facilities: It is also widely used in some living facilities. For example, in electric water heaters, bimetallic electric contact thermometers can be used to control the water temperature inside the water heater. When the water temperature reaches the set maximum temperature, the electric contact disconnects the heating circuit to avoid safety issues caused by excessively high water temperature; When the water temperature drops to a certain level, the electrical contact closes, the heating circuit is connected, and heating continues.
characteristic
Simple and reliable: Its structure is relatively simple, mainly composed of bimetallic sheets and electrical contacts, without complex electronic components. This makes it have good stability in some harsh industrial environments or situations with high reliability requirements. For example, in some factory workshops with complex environments such as dust and humidity, bimetallic electric contact thermometers can work normally.
Low price: Compared to some high-precision and complex temperature sensors and control systems, the cost of bimetallic electric contact thermometers is lower. This makes it widely used in some situations where temperature control accuracy is not extremely high, such as ordinary industrial heating furnaces, small household appliances, and other equipment, which can effectively reduce equipment costs.
Limited accuracy: Its temperature measurement accuracy is generally not as good as high-precision temperature measuring instruments such as thermocouple thermometers and resistance thermometers. The accuracy of bimetallic electric contact thermometers is usually around ± 1- ± 2 ℃, so they are less commonly used in precision chemical and electronic chip manufacturing fields that require extremely high temperature accuracy.
