Source: Beijing Jigao Air Conditioning Repair Phone http://blog.sina.com.cn/jigaokongtiao.
Jigao Air Conditioning Repair Q&A: The working principle of the bimetallic self-recording thermometer
The bimetallic self-recording thermometer is a type of solid expansion thermometer, and its working principle is as follows: The temperature-sensitive element of the self-recording thermometer is made by welding two metal sheets with different linear expansion coefficients together. When the air around the thermometer undergoes biochemical changes, the bimetallic strip bends due to the difference in expansion coefficients, and the degree of bending is proportional to the magnitude of the air temperature change. In the bimetallic self-recording thermometer, after the bimetallic strip A bends, it can produce displacement and drive the recording pointer D through the action of the lever C, recording the situation of air temperature changes on the chart.
A self-recording thermometer can be used to measure and record the changes in air temperature over 24 hours, while also facilitating data collection, making it suitable for air conditioning testing and adjustment work.