Bimetallic thermometer can work under high temperature?

Bimetallic thermometer as a field indicating instrument, widely used in the industry, but many users find bimetallic thermometer met after high temperature, would reduce the accuracy of measurement, what reason is this? Don't bimetallic thermometer is suitable for working under high temperature? Bimetallic thermometer is failed or the limitations of the thermometer itself? So we'll be the first to come to study the working principle of the thermometer. Bimetallic thermometer temperature sensing element is composed of two layers of different linear expansion coefficient, made of sheet metal folding welding together, linear expansion coefficient of large pieces of metal is called the active layer, and the other one is called passive layer, one end of the element is fixed, the other end of the free end, when the measured temperature changes, as a result of the two layers of metal linear expansion coefficient is different, the free end by the combination of torque and bending ( Or deformation) , the change of curvature and physical properties of the bimetallic strip material, length of the thickness of each layer, temperature, and has nothing to do with the width. When temperature is designed, the bimetallic strip of material and geometry size, so the change of curvature is only related to temperature, if on the free end is equipped with drive mechanism, pointer and dial indication in temperature, so you can directly show the temperature value. Through a careful analysis of the above, we will find that because of the thermometer USES a metal material, so there will be a certain limit. The thermal expansion coefficient of metal only can approximate think when in low temperature is constant, the high temperature of 500 ℃ ( 932℉） Above, the thermal expansion coefficient of metal will not remain constant, then to metal heat bilges cold shrink principle of bimetallic thermometer to measure the temperature is not accurate. So the panel can be printed 600 ℃ ( 1112℉） , but the precision can only guarantee to 500 ℃, and cannot be used for a long time in high temperature area.