As an instrument for measuring gas pressure, Air pressu […]
As an instrument for measuring gas pressure, Air pressure gauge is often used to measure atmospheric pressure and is often used in meteorological observation, mountaineering and other fields. There are many ways to measure air pressure, and people have also created Air pressure gauges with different principles, such as mercury barometers, metal box barometers, and so on. Next, we introduce the principle of pressure measurement of several barometers.
Atmospheric Pressure Measurement Method
There are several ways to measure atmospheric pressure:
The first method is to measure the altitude and then calculate the atmospheric pressure according to a formula. The principle of this method is that the atmospheric pressure decreases with the increase of altitude.
The second method is to use the principle of "balance of two forces" and the idea of "equivalent substitution" to measure the atmospheric pressure. That is, let the atmospheric pressure hold a certain length of liquid column (commonly used mercury column), the pressure on the bottom plane of the mercury column is balanced with the atmospheric pressure, and measure the height of the mercury column (using "mm" as the unit), you can use xxx mm of mercury The column represents the atmospheric pressure, and the pressure of the mercury column gravity on the bottom plane can also be calculated, and the pressure value can be used instead of the atmospheric pressure.
The third method is to compress the metal box with atmospheric pressure, measure the compression distance (or convert it into the deflection angle of the pointer), and use the scale corresponding to the changed distance or angle to read the atmospheric pressure.
Mercury Barometric Pressure
The principle of mercury column pressure measurement is that the lower end of the mercury tube of the barometer is inserted into the mercury in the mercury tank, but it is not fixed. The air pressure passes through the mercury in the mercury tank to support the height of the mercury column in the mercury tube. On the other hand, the top plane of the mercury tube also receives the action of air pressure from the outside, but there is no pressure from the inside of the tube, so the pressure on the top of the mercury tube makes the balance The weight on the other end makes it balanced, so the balance moves with the atmospheric pressure, and the change in air pressure can be measured.
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