What is the difference between a small vacuum pump and a large vacuum pump?

What is the difference between a small vacuum pump and a large vacuum pump? Large vacuum pump features: Simply put: power, high ultimate vacuum (absolute pressure is very small) (the absolute pressure is smaller, representing the higher the ultimate vacuum), and some can even do 10 negative side Pa, very close The theory is empty. Pumping rate, usually "L / S (L / s)" as a unit. Industry has a very wide range of applications. Disadvantages: high prices, bulky, heavy weight, high noise, high energy consumption, the need for regular maintenance, not easy to move. Some large vacuum pump must use vacuum pump oil or lubricating oil, the work will produce oil mist, the working medium pollution ...... The above shortcomings in some cases particularly obvious, such as large vacuum pump although the vacuum is high, but in the case of low vacuum wasted , Like a laboratory, only need to pump a small amount of gas for gas sampling, gas analysis, gas circulation, vacuum adsorption, gas transfer, pressurization, indirect absorption of water, drainage, etc., with a large vacuum pump on the contrary exposed many of its shortcomings. This time with a small vacuum pump, the rough vacuum (lower vacuum) can be met, and small size, low noise, low power consumption, easy to operate, easy to carry, maintenance-free, 24 hours continuous operation, but also allows the media is rich in water vapor . Most importantly, because it is dry, oil-free and does not require vacuum pump oil or lubricant, it does not contaminate the working medium and does not interfere with media analysis and more. And the price is much cheaper. Now, with the wide range of applications of small vacuum pumps in various fields and the improvement of vacuum technology, the performance of small vacuum pumps has also been continuously improved. For example, a vacuum pump with high vacuum pressure can even achieve the ultimate vacuum About -0.09Mpa; pumping rate up to: 28L / Min; Also can exhaust, cheer dual-use small vacuum pump, negative pressure (-50KPa), the maximum output positive pressure (relative atmospheric pressure) 100KPa ).