Human activities are filled with air. Although the air is colorless and tasteless, it is invisible to the human eye. In fact, the space around the earth is not empty, and the air is not a "nil" thing. It is like all objects. Space also has weight. At the same time, it is not a single substance, but a mixture of various gases. The environment in which humans live is called the atmosphere, and the pressure they have is called atmospheric pressure. The atmospheric pressure has different values ​​depending on the altitude and weather conditions. The so-called "vacuum" refers to a space state with a pressure lower than atmospheric pressure, that is, a gas state that is lower than atmospheric pressure in a given space. The vacuum space also contains gaseous molecules, but the number of gaseous molecules is less than that under atmospheric pressure. Vacuum exists only with respect to atmospheric pressure. An "absolute vacuum" without any substance at all can never exist.



2. What is vacuum?



Vacuum refers to the difference between the gas pressure in the space and the atmospheric pressure at that time. Generally speaking, "high vacuum" and "good vacuum" refer to low pressure, whereas "low vacuum", "bad vacuum" and "vacuum cannot be drawn" refer to high pressure.






3. What is a "vacuum pump"?



Any equipment that can obtain a vacuum is called a vacuum pump. Such as water flow pump, rotary vane pump, slide valve pump, roots pump, oil booster pump, diffusion pump, molecular pump, ion getter pump, sublimation pump, cryopump, etc. are all vacuum pumps.



4. What is the ultimate pressure?



The ultimate pressure, also called the ultimate vacuum, refers to the highest degree of vacuum that can be obtained in the vacuum obtaining equipment, that is, the lowest pressure. Various types of vacuum pumps have certain limits due to the inherent structure of the vacuum pump. For the determination of the ultimate pressure of mechanical vacuum pump oil, it is stipulated that a two-stage superior-grade vacuum pump must be used as the test pump, otherwise the pump itself will not reach the ultimate pressure specified by the oil index, which will affect the oil test results. Another example is the three-stage glass oil diffusion pump for the ultimate pressure test of the diffusion pump oil, which is also used after strict test selection.



5. What is saturated vapor pressure?



When any liquid is vaporized, the liquid molecules must overcome the gravitational force of the liquid molecules on it in order to escape from the liquid surface and fly to the surrounding space. This phenomenon is called evaporation. Conversely, when a gas is converted into a liquid, it is called condensation.



In a closed space at a certain temperature, if the liquid evaporates and fills the space with vapor of a certain density or pressure, the liquid will no longer evaporate and decrease, at which time the liquid and vapor phases have reached phase equilibrium. This balance is nothing more than constant evaporation and constant condensation. For example, in a closed container with constant temperature, the liquid in the container will automatically evaporate and vaporize until the vapor pressure reaches a certain value. The vapor pressure at this time is called the saturated vapor pressure of the substance at this temperature.

Guangzhou Suwei Electronic Technology Co., Ltd.

Provided by the technical department

2009-2-2