InstrumentationPressure Measurement

# Instrumentation : Basics of pressure measurement

**Pressure measurement **

Pressure is an important process variable.

Pressure is defined as force per unit area.

Pressure = Force / Area

Force can be represented as Pound force,Kilogram force,Newton,dyne

Area can be represented as Square inches,Square feet,Suare Centimeter, Square Meters

**Common units of Pressure **include:

1.Pounds per square inch (psi)

2.Newton/m2 (=Pa) : SI unit

3.KiloPascals(kPa)

Other units:

Inches(or mm) of water(or Hg)

Bar

Atmosphere(1 atm = 760 mm Hg)

Torr (1 mm of Hg)

**Gauge Absolute and Atmospheric pressure**

**Gauge pressure** : Pressure above atmospheric is called gauge pressure.

**Vacuum Pressure**: Pressure below atmospheric is a vacuum (negative gauge pressure)

**Absolute pressure**: Absolute pressure is measured from a perfect vacuum