Misunderstanding of the temperature range of bimetallic thermometer
Release time：2017-10-03 Clicks：872
Bimetallic thermometer is the use of two different temperature expansion coefficient of metal, made into a thermal sensor, make full use of the principle of thermal expansion and contraction, to solve the temperature in the temperature measurement accuracy, in order to improve the sensitivity of bimetallic thermometer temperature, usually The metal sheet is formed into a spiral coil shape, and when the temperature of the multilayer metal sheet is changed, the amount of the metal is expanded or contracted so that the spiral coil is rolled up or loosened, since one end of the spiral coil is fixed and the other end Free rotation of the pointer connected.
Therefore, when the bimetal feel the temperature changes, the pointer can be a circular index on the scale to indicate the temperature, the bimetallic thermometer temperature range is -40 ~ 550 ℃, the allowable error: ± 1.6 degrees The
This creates the following two errors:
1, high temperature range
Bimetallic thermometer temperature range is 200 ~ 650 ℃ (Encyclopedia is also clearly documented), allow the error are about 1% of the scale range. In fact, this is wrong, because this kind of metal sheet made of spiral volume thermal conductivity sensor, 650 ℃ in the case of high temperature fatigue, the temperature difference is very large, so when the temperature exceeds 550 ℃, should consider the use of thermocouple to solve this problem.
2, the minimum temperature range
In the relevant information clearly records: bimetallic thermometer temperature range is 200 ~ 650 ℃ (this is not correct), the minimum temperature can be measured to -40 ℃. In fact, this is not much, because the bimetallic thermometer in the production of temperature calibration is usually -20 ℃ (if the need for low temperature, if not, we usually standard 0 ℃ to the customer to the upper limit of temperature.
