The bimetallic thermometer is a kind of field test instrument for measuring medium and low temperature. It can directly measure the temperature of liquid vapor and gas medium in the range of -80℃ to +500℃ in various production processes. The main component of the industrial bimetallic thermometer is a multilayer metal sheet composed of two or more metal sheets stacked together, using the principle that two different metals expand to different degrees when the temperature changes. When the temperature changes, the free end of the temperature sensing device rotates accordingly, driving the pointer on the thin shaft to produce an Angle change, indicating the corresponding temperature on the dial.
The working principle of bimetal thermometer is the use of two different temperature expansion coefficient of the metal, in order to improve the sensitivity of temperature measurement, usually the metal sheet is made into spiral roll shape, when the temperature of the multi-layer metal sheet changes, each layer of metal expansion or contraction varies, so that the spiral roll up or loosen. Bimetallic thermometers use bimetallic helical materials as temperature sensing elements. The fixed end of the bimetal spiral temperature sensing element is welded on the protective tube, the other end is a free end is connected to the table shaft with a pointer, when the temperature of the measured medium changes, the bimetal spiral temperature sensing element produces a twist, the free end drives the needle to rotate, and directly read the temperature value of the measured medium on the dial.
Because one end of the coil is fixed and the other end is connected to a freely rotating pointer, when the bimetallic sheet senses a change in temperature, the pointer can indicate the temperature on a circular indexing scale. The temperature range of this instrument is -20℃ to +500℃, and the allowable error is about 1.5% of the scale range.
