Bimetallic thermometer in the erroneous zone in the process of use

the bimetallic thermometer using two different expansion coefficient of metal temperature, 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 loose, as a result of the spiral coil end fixed and the other end connected to a free rotating pointer.

as a result, when the bimetallic strip feel the temperature change, Pointers can be on a circular dividing scale to indicate the temperature, the bimetallic thermometer temperature range is - 40 ~ 550 ℃, the permissible error: + / - 1. 6 degrees.

it's form the following two kind of erroneous zone:

1, the high temperature range

bimetallic thermometer temperature range is 200 ~ 650 ℃, permissible error 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, low temperature range

in the related information clear records: bimetallic thermometer temperature range is 200 ~ 650 ℃ ( This is not correct) Low temperature can be measured to - 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.

others say - 80 ℃, also can use double metal thermometer measured! This can be?

bimetallic thermometer is a kind of measurement in the field of low temperature test instrument. Can directly measure the liquid in the process of producing all kinds of steam and gas medium temperature, but to test - Is 80 degrees, heat resistance, if the customer is very insist or site and which can be measured without accuracy requirement.