Bimetal thermometer is a kind of on-site detection instrument suitable for measuring medium and low temperature, which can be used to directly measure the temperature of gas, liquid and steam. The thermometer has the characteristics of waterproof, anti-corrosion, vibration resistance, intuitive, easy to read, no mercury damage, sturdy and durable from the design principle and structure. The bimetal thermometer can automatically send a control signal to cut off the power when the working temperature exceeds a given value. Or call the police. It can replace other types of temperature measuring instruments, and is widely used in petroleum, chemical, machinery, shipbuilding, power generation, textile, printing and dyeing industries and scientific research departments.

Bimetal thermometers work on the principle that two different metals expand at different degrees when the temperature changes. The main component of an industrial bimetal thermometer is a multilayer metal sheet composed of two or more metal sheets laminated together. In order to improve the sensitivity of temperature measurement, the metal sheet is usually made into a spiral shape. When the temperature of the multi-layer metal sheet changes, the amount of expansion or contraction of each layer of metal varies, causing the spiral coil to roll up or loosen. Because one end of the spiral coil is fixed and the other end is connected with a pointer that can rotate freely, when the bimetallic piece feels the temperature change, the pointer can indicate the temperature on a circular graduation scale. This kind of thermometer is similar to the rod-shaped glass liquid thermometer, but it can be used under conditions that require higher mechanical strength.