Reasons for the inaccuracy of bimetal thermometers at high temperatures

Bimetal thermometers encounter high temperatures during measurement, and the reason for the inaccurate temperature measurement is:

The temperature sensing element of the bimetal thermometer is made up of two layers of different linear expansion coefficients, and the metal sheets are stacked and welded together. The metal piece with a large coefficient of linear expansion is called the active layer, and the other piece is called the passive layer. Fixed, the other end is the free end. When the measured temperature changes, the free end will be deformed (or deformed) by the combined moment due to the different linear expansion coefficients of the two metal sheets, and the curvature and composition of the bimetal The physical properties of the material, the length of each layer is related to the thickness, regardless of the width. When the temperature is designed, the material and geometry of the bimetal are determined, so the curvature is only related to the temperature. If the free end is equipped with a transmission mechanism, a pointer and a dial marked with temperature, the temperature can be directly displayed. Indication.

Because the coefficient of thermal expansion of metal can be approximated as a constant only at medium and low temperatures. At high temperatures, the coefficient of thermal expansion of the metal will not be maintained constant. At this time, the bimetallic thermometer made by the principle of thermal expansion and contraction of metal is measured. The temperature is not accurate.