A PNEUMATIC SYSTEM is defined as an application that uses a positive pressure gas to perform an operation. A typical air compressor can generate over 100 psi greater than atmospheric pressure. Since atmospheric pressure at sea level has an expected value of 14.7 psi, pneumatic systems have available pressures of many multiples of atmospheric pressure. A vacuum system is one in which gas is removed to create a pressure lower than atmospheric pressure. Therefore, theoretically, the maximum available vacuum pressure at sea level is -14.7 psi relative to atmospheric pressure. This is a state of "perfect vacuum," in which all gas and matter are removed from the system. It is referred to as absolute pressure.
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