压强的实际物理意义是什么？
状态变量压强（p）的定义是均匀施加到某个表面（A）的压力（Fn）。液体、气体或固体均可施加该种压力。
压力/差压物理原理
压力补偿器示例
根据以上公式，压力相当于校准砝码的重量。p（e=）作用于单位面积上的相对压强，m=砝码的质量，g=重力加速度，A（0）=（有效）横截面。
The pressure units
The pressure unit Pascal (Pa) is derived from the unit of the (weight) force Newton (N), i.e. N je m². One pascal (Pa) corresponds to the pressure acting evenly on a surface when a force of 1 N is exerted vertically on an area of 1 m².
Pascal (Pa)
Measurement in cleanrooms or in flow velicity measurements with Pitot tube.
hPa (= mbar)
Gas flow pressure, gas static pressure
bar, KPa, MPa
Standard units in industrial pressure measuring technology.
mmHg
(= millimeters of mercury) Standard for medical technology (blood pressure) instead of the previous mmH2O.
micron
Smallest unit (750 micron = 1hPa) in the pressure range, e.g. when evacuating refrigeration systems.
Pressure types
Pressure measurement compares an actual pressure with a reference pressure. Pressure measuring technology distinguishes between the following types of pressure, enabling a statement to be made about the relationship between the measuring pressure and the reference pressure. Absolute pressure relates to the vacuous space of the universe (zero pressure).
Absolute pressure
- Measured pressure above absolute zero
- Reference, ideal vacuum
- Measuring pressure is always greater than reference pressure
Differential pressure
- Measured pressure above or below any desired reference pressure
- Measuring pressure is less or greater than reference pressure
Positive pressure
- Measured pressure above the barometric daily air pressure
- Reference ambient pressure
- Measuring pressure is always greater than reference pressure
Negative pressure
- Measured pressure below the barometric daily air pressure
- Reference ambient pressure
- Measuring pressure is always less than reference pressure
Crucial to life: atmospheric pressure
- Atmospheric pressure arises through the weight of the atmosphere that surrounds the earth.