Pressure Gauges

The devices that are used for measuring pressure are called pressure gauges. Gauge pressure is the pressure relative to atmospheric pressure. For the pressures above atmospheric pressure, gauge pressure is positive. For the pressures below atmospheric pressure, gauge pressure is negative. The pressure gauge is also known as pressure meters or vacuum gauges. A device that uses the surface area and weight of a liquid column to measure and indicate pressure is known as a manometer.

Most gauges calculate the pressure relative to atmospheric pressure as the zero point. Hence, this form of reading is known as gauge pressure. Pressure gauges are analog as well as digital.

The pressure difference between the system and the atmosphere is given by the formula:

P=Pa+ ρgh

Where,

P= pressure at any point

Pa = atmospheric pressure

From this, we can make out that the pressure at any point is always greater than the atmospheric pressure by ρgh amount.

When P-Pa=ρgh

Where,

P =pressure of the system

Pa=atmospheric pressure

(P-Pa) = pressure difference between the system and atmosphere.

hρg = Gauge pressure

The difference between two pressures measured using the gauge is known as gauge pressure. Now, let us know more about the types of pressure gauges.