# Pressure definition and Types, Units

Pressure is probably one of the most commonly measured variables in the power **plant**. It includes the measurement of **steam** pressure; feed water pressure, **condenser** pressure, lubricating oil pressure and many more. Pressure is actually the measurement of **force** acting on area of surface. We could represent this as

The units of measurement are either in pounds per square inch (PSI) in British units or Pascals (Pa) in metric. As one PSI is approximately 7000 Pa, we often use kPa and MPa as units of **pressure**.

**Pressure Measurement :**

This module will examine the theory and operation of pressure detectors (**bourdon** tubes, **diaphragms**, **bellows**, forced balance and variable **capacitance**). It also covers the variables of an operating environment (pressure, temperature) and the possible modes of failure.

# Difference between absolute pressure and gauge pressure

**What is gauge pressure.**

The pressure of a system above the atmospheric pressure is called gauge pressure. Gauge pressure can calculated if the absolute and atmospheric **pressures** are known by using the

**Formula: Pgauge = Pabs – Patm**

**What is absolute pressure**

Absolute pressure is a pressure that is relative to the zero pressure in the empty, air-free space of the universe. This reference pressure is the ideal or absolute vacuum.

**What is differential Pressure **

Differential-pressure (DP) measure the difference between two pressures and can be used for measure pressure or level