Positive pressure pump and negative pressure pump what is the difference and contact

There are many miniature vacuum pumps, micro air pump, micro gas sampling pump, micro gas circulation pump, miniature suction pump, micro suction pump, mini pump, miniature pump, miniature high pressure pump. Some of them are positive pressure pump, some negative pressure pump, how to distinguish it? In general, micro-pump has both intake and exhaust ports, the inlet can produce less than atmospheric pressure (ie atmospheric pressure) called "negative pressure"; in the exhaust can produce more than atmospheric pressure Called "positive pressure"; for example, often say that the vacuum pump is negative pressure pump, booster pump is positive pressure pump. The difference: Positive pressure pump and negative pressure pump are very different. For example, the gas flow, the negative pressure pump is the external gas is sucked into the suction nozzle; positive pressure is discharged from the exhaust nozzle; such as the level of pressure. In fact, "negative pressure pump", "positive pressure pump" is mainly from the function and the main purpose of people to distinguish. "Negative pressure pump" is mainly used in vacuum (negative pressure) requirements of the occasion, such as: gas extraction, gas analysis, gas recycling, gas sampling, vacuum adsorption, indirect water absorption; and "positive pressure pump" is mainly used for the needs Pump as a motive force, the gas transfer, the pressure on the closed container, inflatable cheer, indirect pressure water, both commonly used in medical, scientific research, environmental protection, equipment, control and so on.