Pressure sensor
From Wikipedia, the free encyclopedia
A pressure sensor measures the pressure, typically of fluids. Pressure, of course, is an expression of the force required to stop a fluid from expanding, and is usually stated in terms of force per unit area. A pressure sensor generates a signal related to the pressure imposed. Typically, such a signal is electrical, but it might also include additional means, such as optic signals, visual signals and/or auditory signals.
Pressure sensors have particular utility for monitoring the pressure in a fluid network. As compared with flow sensors, pressure sensors often require less cost to achieve a similar result. Pressure sensors are often fabricated using thin membranes that flex under pressure.
Some pressure sensors function in a binary manner, i.e., when pressure is applied to a pressure sensor, the sensor acts to complete or break an electical circuit. Some speed cameras use them.
[edit] Types of fluid pressure measurements
Absolute Pressure
Absolute pressure is expressed relative to a vacuum (i.e., no pressure). Atmospheric pressure, is about 100kPa (14.7 psia) at sea level. Atmospheric pressure is an absolute pressure.r
Gauge Pressure
Gauge pressure is expressed relative to atmospheric pressure.
A vented gauge pressure sensor has one port uncovered so it may operate to sense the local atmospheric pressure. A sealed gauge pressure sensor has one port sealed at manufacture at average atmospheric pressure.
An example of gauge pressure would be a tire pressure gauge. When the tire pressure gauge reads 0 psig, there is really 14.7 psia (atmospheric pressure) in the tire.
Differential Pressure
A differential pressure sensor expresses the difference in pressure between two ports on the device. The tire pressure gauge example, given above, is an example of the differential pressure between the absolute pressure of the atmosphere and the gauge pressure in the tire.
