At2 H 21 Pressure Sensor Improved

DEPT. of ELECTRICAL EQUIPMENT AND INSTALLATION TECHNOLOGY AT - A UTOMA TION TECHNOL OGY PRESSURE SENSORS 1.0 Parameter of pressure : Pressure is define as the amount of force applied to an area. In mathematically as pressure is equal to force per unit area : P = F/ A Amount of Force

F – Force A – Area 1 psi = 51.714 mmHg = 2.0359 in.Hg = 27.680 in.H2O = 6.8946 kPa 1 bar = 14.504 psi 1 = 14.696 psi atm.

Unit for pressure is pound per square inch ( psi ). Pressure measurement uses amount of atmospheric of air pressure caused by the atmosphere at sea level is 14.7 psi. Anything below than atmosphere pressure is called vacuum. The value of vacuum is from 14.7 – 0 psi . 2.0 Type of analogue pressure sensor 2.1 Mechanical pressure sensor 2.1.1 Bourdon Tube The most common pressure sensor is Bourdon Tube . The simplest is Bourdon Tube is C- shaped metal tube. ( refer to figure 9a ). One end is sealed and the other end is connected to source of pressure. When pressure is applied to the inside of the tube, the sealed end tends to straighten out which cause a small movement at the sealed end. This movement can be amplified by gears or transferred to a linear potentiometer which convert the pressure value to resistance. There are two type of Bourdon Tube such as Helical and Spiral type Bourdon Tube. Bourdon Tube sensors are used to measure pressure up to 100, 000 psi. 2.1.2 Diaphragm Pressure sensor

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AT2-222 – Sensors & Fiber Optic Technology Chap.21 – Pressure sensors

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DEPT. of ELECTRICAL EQUIPMENT AND INSTALLATION TECHNOLOGY AT - A UTOMA TION TECHNOL OGY This type of sensor is designed to measure lower pressures in the range of 330 psi and vacuum to 29.9 in.Hg. It is made of a flexible membrane ( made of rubber or metal ). When pressure is applied to the chamber, the diaphragm will expand slightly into the open chamber.

2.1.3 Bellows Pressure sensor This type of sensor is made of sealed chamber that has a multiple ridges like the pleats of an accordion that are compressed slightly. When pressure is applied to the chamber, the chamber will try to expand and open the pleats. This type of sensor is used for pressure less than 30 psi.

Figure 9. The basic pressure sensing element can be configured as a C-shaped Bourdon tube (A); a helical Bourdon tube (B); flat diaphragm (C); a convoluted diaphragm (D); a capsule (E); or a set of bellows (F

Other type of pressure sensors sensors : Handout

AT2-222 – Sensors & Fiber Optic Technology Chap.21 – Pressure sensors

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DEPT. of ELECTRICAL EQUIPMENT AND INSTALLATION TECHNOLOGY AT - A UTOMA TION TECHNOL OGY i. ii. iii.

iv. v.

Differential Pressure sensor strain gauge. Piezoelectric pressure sensor Capacitive pressure sensors Ultrasonic pressure sensors.

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AT2-222 – Sensors & Fiber Optic Technology Chap.21 – Pressure sensors

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