Definition of pressure
Pressure is defined as normal force exerted by a fluid on per unit area.
Counterpart of pressure in solids is normal stress.
SI unit of pressure is pascal (Pa).
1 Pa = 1 N/m2
N is newton
m is meter
Units of pressure
Types of pressures
There are three main types of pressures
Absolute pressure is measured against absolute vacuum.
Gauge pressure is measured against atmospheric pressure.
Vacuum pressure is the negative value of gauge pressure i.e. when actual pressure is below atmospheric pressure.
Relations between above mentioned three types of pressures are given below.
Pgauge = Pabs – Patm
Pvac = Patm – Pabs
Classification of pressure measurement devices
Pressure measurement devices can be broadly divided into following two types.
- Mechanical devices
- Electromechanical devices
Mechanical devices can further be divided into following two types.
- Static pressure measurement devices
- Dynamic pressure measurement devices
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