Methods for expressing pressure: There are two methods for expressing pressure. One is the pressure expressed with absolute vacuum as the benchmark, which is called absolute pressure. The other is the pressure expressed with atmospheric pressure as the benchmark, known as relative pressure. Since most pressure measuring instruments measure relative pressure, relative pressure is also called gauge pressure. When the absolute pressure is less than atmospheric pressure, it can be represented by the value of the absolute pressure inside the container being less than one atmosphere, which is referred to as "vacuum degree." Their relationships are as follows:
Absolute Pressure = Atmospheric Pressure + Relative Pressure
Vacuum Degree = Atmospheric Pressure - Absolute Pressure
The legal unit of pressure in our country is Pa (N/㎡), called Pascal, abbreviated as Pa. Due to this unit being too small, the unit MPa (MegaPascal), which is 10^6 times larger, is often used.
2.5 Elastic Sensitive Elements: Bourdon Tubes, Bellows, Diaphragms
Bourdon Tube Pressure Gauge: The Bourdon tube sensitive element is a C-shaped elastic tube bent into a circular shape with an elliptical cross-section. The pressure of the measuring medium acts on the inner side of the Bourdon tube, causing its elliptical cross-section to tend towards a circular one. Due to the slight deformation of the Bourdon tube, a certain hoop stress is formed, causing the Bourdon tube to extend outward. Since the head of the elastic Bourdon tube is not fixed, it will undergo a slight deformation, the extent of which depends on the pressure of the measuring medium. The deformation of the Bourdon tube is indirectly displayed by the pointer through the movement mechanism, indicating the pressure of the measuring medium.
Capsule Pressure Gauge: The capsule sensitive element consists of two wave-shaped diaphragms connected together. The pressure of the measuring medium acts on the inside of the capsule chamber, and the resulting deformation can be used to indirectly measure the pressure of the medium. The magnitude of the pressure is indicated by the pointer. Capsule pressure gauges are generally used to measure gas pressure and can also measure micro-pressure and provide overpressure protection to some extent. When several capsule sensitive elements are stacked together, they can generate a greater transmission force to measure extremely small pressures.
2.6 Radial Type, Axial Type
Radial Type: Refers to the connection port of the pressure gauge being perpendicular to the dial (I-type).
Axial Type: Refers to the connection port of the pressure gauge being parallel to the dial (T-type).