The two concepts of theoretical vacuum and ultimate vacuum are similar in meaning and are often used in industrial vacuum equipment such as miniature vacuum pumps, miniature gas pumps, micro gas sampling pumps, miniature suction pumps, micro gas circulation pumps, and the like. The vacuum pump connected to the test container, after sufficient time continuous suction, the pressure in the container no longer continue to decline and maintain a certain value, then the gas pressure in the container is the absolute pressure of the pump. When the pressure value is as small as 0, the so-called theoretical vacuum and ultimate vacuum indicate that there is no substance (including molecules, atoms, etc.) present in this state, which is only theoretically existed and practically impossible . The smaller the pressure value, that is, the higher the vacuum, indicating that the closer to the theoretical vacuum, the ultimate vacuum, the pump vacuum performance is better, but the corresponding material life, sealing conditions, precision machining parts, etc. are also greatly increased. With the development of instrumentation industry and people's environmental protection requirements, the demand for miniature vacuum pumps with relatively low cost, oil-free and pollution-free, low power consumption and compact size has been increasing. For example, there is a PC3025N miniature vacuum pump with high performance-price ratio, which can run continuously for 24 hours. Its life expectancy, reliability, stability and various performance indexes are high, and can be customized into various special applications (low interference type, high temperature type, etc.) .