What is pressure measurement and its principle？

In physical concepts, pressure is a force acting vertically on a unit area. It is one of the important parameters in industrial production. In pressure measurement, it is often divided into maximum pressure, gauge pressure, negative pressure and vacuum degree. The so-called maximum pressure refers to the total pressure of the measured medium acting on the unit area of the container, represented by the symbol Pj. The average pressure generated by the air column on the ground is called atmospheric pressure, represented by Pq. **The difference between pressure and atmospheric pressure is called gauge pressure and is represented by Pb. That is, Pb=Pj-Pq. When the maximum pressure value is less than the atmospheric pressure value, the gauge pressure is a negative value (ie, negative pressure). The maximum value of this negative pressure value is called the vacuum degree, represented by Pz.
According to the measurement principle, it is divided into two types:
• Directly measure the force per unit area based on the definition of pressure.
Example: liquid column type, elastic type
• Apply various physical effects produced by pressure acting on an object to achieve pressure.
Example: Resistive: It is a resistor made of metal conductors or semiconductors, and its resistance changes with changes in pressure.
Piezoelectric effect: When a crystal is mechanically deformed under pressure, opposite charges are generated on its two opposite sides.