The production principle of glass rod thermometer

Glass rod thermometer USES temperature measuring principle of heat bilges cold shrink effect: when the temperature changes, the glass rod in the liquid volume expansion or contraction, will happen to change into the liquid column height in capillary, which indicates the temperature from the scale of change. In making glass rod temperature time, the sensitivity of the control is very important. Glass rod thermometer calibration resolution associated with sensitivity, sensitivity, is the scale of the thermometer resolution is high. To improve the sensitivity of the thermometer, can increase the volume of fluid and decreasing the diameter of the capillary. But increase the volume of fluid, not easy to achieve thermal equilibrium with the tested material, cause large lag error, and easily make the ball ministry produces deformation; Decreased capillary diameter can make is not easy to processing capillary evenly, causing fluid column rise unevenly, affect the measuring accuracy. Therefore, we should take the appropriate sensitivity. In addition, the sensitivity of the thermometer and temperature measuring the difference between the fluid and thermal expansion coefficient of glass, and is proportional to the. Usually choose coefficient of thermal expansion larger liquid as liquid temperature, and the thermal expansion coefficient of the glass shall be as small as possible. The commonly used temperature liquid mercury and alcohol.