Why is the mercury column in the thermocouple unable to automatically lower?
The commonly used mercury thermocouple is made based on the principle of hot, cold contraction of mercury. Thermometers are used to measure general temperature, such as measuring room temperature, outside room temperature, measuring water and pool temperatures, etc.; the mercury column of these thermometers is subject to changes in ambient temperature that reflect Immediately, up or down automatically. After using it, the human thermocouple must wave several times, vigorously to lower the mercury column. The mystery in this story is that, in general, the inner diameter of the thermometer glass tube is the same size, and the inner diameter of the thermocouple glass tube has to go through a special design.
Its characteristics are the junction between the mercury column and the particularly small mercury bulb. Because of this design, mercury in the thermocouple’s bulb can be easily extruded from the small gap when subjected to thermal expansion. Also encountered when subjected to cold contraction, the mercury column could not withdraw from that gap smoothly. Still, under the contraction of the inner focusing force of mercury itself, the mercury column immediately broken into two segments at the narrow gap. The upper end of the upper section still indicates body temperature.
In contrast, the lower end is subject to the inner focusing force’s contraction that cannot automatically flow back to the mercury bulb. Because of such design and manufacture, physicians can accurately measure the body’s temperature and diagnose the disease accurately. If the thermocouple is the same as the conventional thermocouple, which just leaves the body and the column of mercury immediately changes (falling right down), the thermocouple loses its practical value.
The thermocouple, after use, may wish its head down, waving hands several times. That’s how to take advantage of inertia, causing the upper section’s mercury to rush through the narrow gap back to the mercury bulb. When waving your hands, some things must also pay attention to the direction and level of strength to achieve a good effect.