WSS - 411 bimetallic thermometer can work under high temperature?

Believe that the WSS - is known to all Bimetallic thermometer can measure in 411, the low temperature of liquid and gas, but some customers of bimetallic thermometer will be used in high temperature environment, the instrument measuring failure, unable to properly measure, what is the cause of this situation? WSS - Bimetallic thermometer is made up of two pieces of sheet metal folding 411 welded together, 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 deformation. 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. From producing and working principle of bimetallic thermometer can understand that the thermal expansion coefficient of metal can approximate thought only when in low temperature is constant, by high temperature, the thermal expansion coefficient of metal will not remain constant, so in this case the bimetallic thermometer is sure to appear measurement fault. In the use of WSS - 411 bimetallic thermometer must be more careful, avoid the blind measurement, it's best to start to test the thermometer, in understanding the bimetallic thermometer temperature measurement range before concrete work.