Basic Terms of Pressure Gauges

1. Positive Pressure and Negative Pressure

2. Relative Pressure and Absolute Pressure

3. Vacuum Degree

4. Methods of Pressure Representation

5. There are two ways to express pressure: one is the pressure expressed with absolute vacuum as the reference, called absolute pressure; the other is the pressure expressed in terms of atmospheric pressure, called relative pressure. Since the pressure measured by most pressure gauges is relative pressure, relative pressure is also known as gauge pressure. When the absolute pressure is less than atmospheric pressure, it can be expressed as a value of absolute pressure in the container that is less than one atmosphere. This is called "vacuum degree".

6. Their relationship is as follows:

Absolute Pressure = Atmospheric Pressure + Relative Pressure

Vacuum Degree = Atmospheric Pressure - Absolute Pressure

7. The legal unit of pressure in China is Pa (N/㎡), known as Pascal, abbreviated as Pa. Since this unit is too small, it is often expressed in its 10^6 times unit, MPa (megapascals).