The working principle of glass thermometer is based on the property of thermal expansion and contraction. When the temperature rises, the liquid in the glass tube (usually alcohol or mercury) expands and its volume increases; when the temperature drops, the liquid contracts and its volume decreases. The temperature is determined by measuring the volume change of the liquid.
The principle of calibration is to use standard substances with known temperatures, such as ice - water mixture (0℃), boiling water (100℃), etc., to compare the thermometer reading with the standard temperature. If the thermometer reading is not consistent with the standard temperature, the scale of the thermometer needs to be adjusted to accurately reflect the temperature.
In the actual calibration process, factors such as the accuracy of the thermometer, measurement errors, and environmental factors also need to be considered. For example, the glass tube of the thermometer may have slight unevenness, which will affect the accuracy of the thermometer; the temperature and humidity of the measurement environment will also have an impact on the measurement results of the thermometer.