Bimetallic thermometer is the most easy to use error? Do you have a gun

The use of bimetallic thermometer myth bimetallic thermometer is a kind of measuring instrument in the field of low temperature detection, has a certain application in many industries. Bimetallic thermometer is in the process of use will form the myth, the myth will seriously affect the use of the bimetallic thermometer. So what is myth? Below small make up to introduce specific. Bimetallic thermometer is the use of two kinds of different temperature of metal expansion coefficient, thermal conductivity sensor is made of, make full use of the principle of heat bilges cold shrink, solved the temperature in the process of temperature measurement accuracy, in order to improve the bimetallic thermometer temperature measurement sensitivity, will usually made of metal spiral coil shape, when multi-layer metal temperature change, the layers of metal expansion or contraction, makes the spiral coil rolled up or let go, because the end fixed and the other end of the spiral coil and connected to the free rotation of a pointer. Therefore, when the bimetallic strip feel the temperature change, Pointers can indicate the temperature on the circular, the bimetallic thermometer is - temperature measurement range 40 ~ 550 ℃, the permissible error: & plusmn; 1. 6 degrees. The following this is formed by two kinds of error: 1, high temperature range: bimetallic thermometer temperature measuring range is - 40 ~ 650 ℃, the margin of error is about 1% of the scale range. In fact this is wrong, because, this made of metal spiral roll shape of thermal conductivity sensor, under the condition of 650 ℃ high temperature fatigue, temperature difference is very big, so when the temperature exceeds 550 ℃, should consider the thermocouple is used to solve this problem. 2. Minimum temperature range: bimetallic thermometer temperature measuring range is - 20~650℃（ This is not correct) , the minimum temperature should be detectable 40℃。 In fact this is not much, because, bimetallic thermometer in - usually a kind of temperature calibration in production 20℃。