In PSA nitrogen (oxygen) equipment, pressure gauges are common. We need to use these instruments to detect, measure, observe, and calculate the pressure in the equipment, or through the associated settings of the instruments to achieve automatic control of the equipment and the realization of functions such as control, alarm and signal transmission.

Since the value in the pressure gauge reflects the pressure of the gas, is the pressure value on the pressure gauge we see in the PSA nitrogen (oxygen) system the true pressure of the gas? In fact, this is not the case. The measured pressure seen here is the difference between the actual pressure (absolute pressure) and the surrounding atmospheric pressure. When the actual pressure is higher than atmospheric pressure, the measured pressure is called gauge pressure. When the actual pressure is lower than atmospheric pressure, the measured pressure is called vacuum, or negative pressure. The relationship between them can be expressed as follows;

Absolute pressure = gauge pressure + atmospheric pressure

Absolute pressure = atmospheric pressure - degree of vacuum

For example, if the gauge pressure is 0.35Mpa and the atmospheric pressure is approximately 0.1MPa, then it can be calculated according to the above formula;

The absolute pressure is, 0.35MPa+0.1MPa=0.45MPa.