Presentation Aerolab1 Session7

7/28/2019 Presentation Aerolab1 Session7

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Pressure Transducers

Are Lab1

Fariba A alli

Amirkabir University of Technology


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Pressure sensor

A pressure sensor measures pressure, typically of

gases or qu s. A pressure sensor generates a signal related to the

.

Typically, such a signal is electrical, but optical,, .

Pressure sensors can also be used to indirectlymeasure other variables such as fluid/ as flowspeed, water level, and altitude.


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Pressure sensor Pressure sensors can alternatively be calledpressure

transducers ressure transmitters ressure sensers

andpressure indicators, among other names. There is also a category of pressure sensors that are

very high speed changes in pressure.

Example applications for this type of sensor would bein the measuring of combustion pressure in an enginecylinder or in a gas turbine. These sensors arecommonl manufactured out of iezoelectric

materials such as quartz.


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Types of pressure measurementsAbsolute pressure sensor

pressure (0 PSI or no pressure). Atmospheric pressure, is 101.325kPa (14.7 PSI) at sea level with reference to vacuum.

Gau e ressure sensor

This sensor is used in different applications because it can becalibrated to measure the pressure relative to a given atmospheric

pressure at a given location. A tire pressure gauge is an exampleo gauge pressure n ca on. en e re pressure gauge rea s0 PSI, there is really 14.7 PSI (atmospheric pressure) in the tire.

Vacuum pressure sensor

s sensor s use o measure pressure ess an e a mosp er cpressure at a given location.


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Types of pressure measurementsDifferential pressure sensor

pressures introduced as inputs to the sensing unit, for example,measuring the pressure drop across an oil filter. Differential

vessels.

Sealed pressure sensor s sensor s t e same as t e gauge pressure sensor except t at t

is previously calibrated by manufacturers to measure pressurerelative to sea level pressure (14.7 PSI).


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Different technologies used in making pressure sensors

Fiber optic sensors

light propagating in a fiber such that it can be used to formsensors. Pressure sensors can be made by constructing

m n a ur ze er op c n er erome ers o sense nanome er

scale displacement of membranes. Pressure can also be made

to induce loss into a fiber to form intensity based sensors.

Mechanical deflection

This technology uses the mechanical properties of a liquid to

measure s pressure. uc as, e e ec o pressure on aspring system and the changes of compression of spring can be

used to measure pressure.


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Different technologies used in making pressure sensors

Semiconductor piezoresistive

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

Strain gauge

materials experience due to change in its stretch or strain. Thistechnology makes use of the change of conductivity of material when

experiencing different pressures and calculates that difference and

maps it to the change of pressure.

Vibrating elements (silicon resonance, for example)

the different materials elements due to change in pressure to calculatethe pressure.


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Strain au eone of the most common is the strain-gage base transducer. The conversion

of pressure into an electrical signal is achieved by the physical deformation

o stra n gages w c are on e nto t e ap ragm o t e pressure

transducer and wired into a Wheatstone bridge configuration. Pressureapplied to the pressure transducer produces a deflection of the diaphragm

.

resistance change proportional to the pressure.


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A lications Pressure sensing

This is the direct use of pressure sensors to measure pressure. This is useful inweather instrumentation, aircraft, cars, and any other machinery that haspressure functionality implemented.

Altitude sensingThis is useful in aircraft, rockets, satellites, weather balloons, and many other

applications. All these applications make use of the relationship between.

following equation:

This equation is calibrated for an altimeter, up to 36,090 feet (11,000 m).


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St les of Pressure Transducers PC Board Mountable Pressure Transducers

compact economical pressure transducers designed to mounton an electrical PC board and be integrated into other products.


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St les of Pressure Transducers General Purpose Transducers

since they are designed to fit the broadest set of applications.


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St les of Pressure Transducers High Stability/High Accuracy Pressure

Most pressure transducers feature an accuracy of 0.25% of fullscale or higher. High stability and high accuracy pressure

rans ucers can o er errors as ow as . o u sca e,

depending on model. Although more expensive than general

purpose transducers, they may be the only option if highprecision is required.


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Styles of Pressure Transducers

Miniature Pressure Transducers

that have very limited space.


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Ome a Com an

PX138-0.3D5V


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Ex erimental Facilit A/D board

Daughter board Wind tunnel

Pressure gauge


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Calibration

0.6000

0.7000

0.3000

0.4000

0.5000

Voltage

0.1000

0.2000

0.0000

0 100 200 300 400 500 600

P(pas)


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Pressure ports distributions


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Thanks for your attentionsThanks for your attentions

Presentation Aerolab1 Session7

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