The application of the bimetallic thermometer

Bimetallic thermometer is a kind of measurement in the field of low temperature test instrument. The instrument is to use two kinds of different expansion coefficient of metal temperature, thermal conductivity sensor is made of, make full use of the principle of heat bilges cold shrink when multi-layer metal temperature change, the layers of metal expansion or contraction, makes the spiral coil rolled up or loose, as a result of the spiral coil end fixed and the other end connected to a free rotating pointer. Therefore, when the bimetallic strip feel the temperature change, Pointers can be in a circular dividing scale to indicate the temperature on the bimetallic thermometer is - temperature measurement range 40 ~ 550 ℃, the permissible error: + / - 1. 6 degrees. This produces the following two kind of erroneous zone: 1, high temperature range bimetallic thermometer temperature range is 200 ~ 650 ℃ ( Baidu encyclopedia is explicitly specify) To allow errors are 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, the lowest temperature range bimetallic thermometer temperature range is 200 ~ 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℃( If you need low temperature, if you don't need, we usually will mark to the limit of temperature 0 ℃ to customers, users are sometimes used - party in Beijing area 40 ℃, this is can do, but in - Under the condition of 40 ℃ to consider whether to accept this error.