User:Kmashal/Pressure Sensors

Pressure sensors classifications
Pressure sensors can be classify in term of pressure ranges they measures, Temperature ranges of operation, and most important the type pressure they measurer. In term of pressure type, we can categorize them in five categories:

1.	Absolute pressure sensor

This pressure sensor measures the pressure relative to perfect Vacuum (0 PSI). 2.	Gauge pressure sensor

We see this pressure sensor used in a lot of applications because it can be calibrated to measure the pressure relative to a given atmospheric pressure at a given location. 3.	 Vacuum pressure sensor

This pressure sensor is used to measure pressure less that the atmospheric pressure at a given location.

4.	Differential pressure sensor

This pressure sensor measure the difference between two or more pressures introduced as inputs to the sensing unit. 5.	Sealed pressure sensor

This pressure sensor is the same as Gauge pressure sensor except its previously calibrated by manufactures to measure pressure relative to sea level pressure (14.6 PSI).

Different technologies used in making pressure sensors
1.	Mechanical deflection

This technology will use the mechanical properties of a liquid to measure its pressure. 2.	Strain gauge

This technology makes use of the changes in resistance that some materials experiences due to change in its stretch or strain.

3.	Semiconductor Piezoresistive

This technology uses the change in conductivity of the semiconductors due to the change in pressure to measure the pressure.

4.	Microelectromechanical systems (MEMS)

This technology combines microelectronics with tiny mechanical systems such as, valves, gears, and any other mechanical systems all on one semiconductor chip using Nanotechnology to measure pressure.

5.	Vibrating elements (silicon resonance, for example)

This technology uses the change in vibration of the different materials elements due to change in pressure to calculate the pressure.

6.	Variable capacitance

The technology uses the change of capacitance due to change of the distance between the plates of the capacitor because of change in pressure to calculate the pressure.

Applications
There are wide applications for pressure sensors but we can narrow it down to two major categories:

1.	Pressure sensing We see it application in weather instrumentation, aircraft, cars, and any other machinery has pressure functionality implemented such as food manufacturing machines. 2.	Altitude sensing

We see its application in aircraft, rockets, satellites, weather balloons, and many other applications. All these applications make use of the relationship between change in pressure as we change the altitude which is govern by the following equation :


 * $$h = \frac{(1-(P/P_{ref})^{0.19026}) \times 288.15}{0.00198122}$$

This equation calibrated for an altimeter, up to 36,090 feet (11,000 m), outside that range an error will be introduced which can be calculated differently for each different pressure sensor. These error calculations will factor in the error introduced by the change in temperature as we go up.