Pressure sensor

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A pressure sensor is a device for measuring gas or liquid pressure. Pressure is the expression of the force required to stop fluid from expansion, and is usually expressed in units of force per unit area. Pressure sensors usually act as transducers; it produces a signal as a function of the applied pressure. For the purposes of this article, such a signal is electricity.

Pressure sensors are used for control and monitoring in thousands of everyday applications. Pressure sensors can also be used to indirectly measure other variables such as fluid flow/gas, speed, water level, and altitude. Pressure sensors can be alternately called pressure transducers , pressure transmitters , pressure senders , pressure indicators , piezometers and manometers , among other names.

Pressure sensors can vary drastically in technology, design, performance, app compatibility, and cost. The conservative estimate is that there may be more than 50 technologies and at least 300 companies that create pressure sensors around the world.

There is also a category of pressure sensors designed to measure in dynamic mode to capture very high speed changes in pressure. Examples of applications for this type of sensor will be in the measurement of the combustion pressure in the engine cylinder or in the gas turbine. These sensors are generally made of piezoelectric materials such as quartz.

Some pressure sensors are pressure switches, which light up or die at certain pressures. For example, a water pump can be controlled by a pressure switch so that it starts when water is released from the system, reducing the pressure in the reservoir.

Video Pressure sensor

Jenis pengukuran tekanan

Pressure sensors can be classified based on the range of pressure they measure, the operating temperature range, and most importantly the type of pressure they measure. Pressure sensors are named differently according to their purpose, but the same technology can be used with different names.

• Absolute pressure sensor

This sensor measures relative pressure on perfect vacuum.

• Gauge pressure sensor

This sensor measures relative pressure on atmospheric pressure. The tire pressure gauge is an example measuring gauge pressure; when indicating zero, the pressure measured is equal to the ambient pressure.

• Vacuum pressure sensor

This term can cause confusion. It can be used to describe sensors that measure pressure under atmospheric pressure, indicating the difference between low pressure and atmospheric pressure, but can also be used to describe sensors that measure absolute pressure relative to the vacuum.

• Differential pressure sensors

This sensor measures the difference between two pressures, one connected to each side of the sensor. Differential pressure sensors are used to measure many properties, such as pressure drops through oil filters or air filters, liquid levels (by comparing pressure above and below liquid) or flow rate (by measuring pressure changes across boundaries). Technically, most pressure sensors are differential pressure sensors; for example the measuring pressure sensor is simply a differential pressure sensor where one side is open to the ambient atmosphere.

• The sealed pressure sensor

This sensor is similar to a gauge pressure sensor except that it measures the pressure relative to some fixed pressure rather than ambient atmospheric pressure (which varies according to location and weather).

Maps Pressure sensor

Pressure sensor technology

There are two basic categories of analog pressure sensors,

Power collector type This type of electronic pressure sensor generally uses a force collector (such as a diaphragm, piston, Bourdon tube, or bellows) to measure strain (or deflection) due to forces applied to an area (pressure). ).

• Piezoresistive strain gauge

Using the piezoresistive effect of bonded strain gauges or formed to detect strain due to applied pressure, increased resistance when pressure damages the material. Common technology types are Silicon (Monocrystalline), Polysilicon Thin Film, Bonded Metal Foil, Thick Film, Silicon-on-Sapphire and Sputtered Thin Film. Generally, strain gauges are connected to form a series of Wheatstone bridges to maximize the output of the sensor and to reduce the sensitivity to error. This is the most commonly used sensing technology for general purpose pressure measurements.

• Capacitive

Using a diaphragm and pressure cavity to make a variable capacitor to detect the tension due to applied pressure, decrease the capacitance when pressure destroys the diaphragm. Common technologies use metal diaphragms, ceramics, and silicon.

• Electromagnetic

Measures the displacement of the diaphragm by means of changes in inductance (reluctance), LVDT, Hall Effect, or by eddy current principle.

• Piezoelectric

Using piezoelectric effects on certain materials such as quartz to measure pressure on pressure sensing mechanisms. This technology is commonly used for very dynamic pressure measurements.

• Strain-Gauge

Strain-based pressure gauges also use pressure sensitive elements in which a metallic strain gauge is attached or a thin film meter is applied using sputtering. This measuring element may be a diaphragm or a metallic foil gauge in canned type can also be used. The great advantage of this monolithic can-type design is the increased stiffness and ability to measure the highest pressure up to 15,000 bar. Electrical connections are usually made through the Wheatstone bridge allowing for a good amplification of the signal and the exact and constant measurement results.

• Optics

Techniques include the use of physical changes in optical fibers to detect tension due to applied pressure. A common example of this type is Grating Fiber Bragg. This technology is used in challenging applications where measurements may be very remote, under high temperatures, or may benefit from technologies that are inherently immune to electromagnetic interference. Other analogue techniques use elastic films made in layers that can change the reflected wavelength according to the applied pressure (strain).

• Potentiometry

Use the wiper motion along the resistive mechanism to detect the tension caused by the applied pressure.

More types

This type of electronic pressure sensor uses other properties (such as density) to infer gas, or liquid pressure.

• Resonance

Using a resonance frequency change in the sensing mechanism to measure stress, or changes in gas density, caused by applied pressure. This technology can be used in conjunction with style collectors, like those in the above categories. Alternatively, resonance technology can be used by exposing the resonant element itself to the media, where the resonant frequency depends on the media density. The sensors have been made from vibrating wire, vibrating cylinder, quartz, and silicon MEMS. Generally, this technology is considered to provide very stable readings from time to time.

• Thermal

Uses changes in thermal conductivity of the gas due to density changes to measure pressure. A common example of this type is the Pirani gauge.

• Ionization

Measures the flow of charged gas particles (ions) that vary due to density changes to measure pressure. Common examples are the Heat and Cold Cathode gauges.

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Apps

There are many applications for pressure sensors:

• Pressure sensing

This is where the measurement of interest is pressure, expressed as the force per unit area. This is useful in weather instrumentation, airplanes, cars, and every other machine that has a pressure function implemented.

• Height sensing

This is useful in aircraft, rockets, satellites, weather balloons, and many other applications. All of these applications utilize the relationship between pressure changes relative to altitude. This relationship is governed by the following equation:

$Â\; ÂÂ\; Â\; Â\; ÂÂ\; Â\; Â\; Â\; Â{\displaystyle Â\; Â\; Â\; Â\; Â\; Â\; Â\; ÂhÂ\; Â\; Â\; Â\; Â\; Â\; Â\; Â=()\; Â\; Â\; Â\; Â\; Â\; Â\; Â\; Â1Â\; Â\; Â\; Â\; Â\; Â\; Â\; Â-()\; Â\; Â\; Â\; Â\; Â\; Â\; Â\; ÂPÂ\; Â\; Â\; Â\; Â\; Â\; Â\; Â/Â\; Â\; Â\; Â\; Â\; Â\; Â\; ÂÂ\; Â\; Â\; Â\; Â\; Â\; Â\; ÂP_{Â\; Â\; Â\; Â\; Â\; Â\; Â\; Â\; Â\; Â\; Â\; Â}}$ mi mathvariant = "normal"> r               e               f                                                 )                      0.190284                           )         ÃÆ' -         145366.45                   f           t                   Annotation encoding = "application/x-tex"> {\ displaystyle h = (1- (P/P _ {\ mathrm {ref}}) ^ {0.190284}) \ times 145366.45 \ mathrm {ft} }  Â

This equation is calibrated for altimeter, up to 36,090 feet (11,000 m). Beyond that range, errors will be introduced which can be calculated differently for each different pressure sensor. The calculation of this error will be a factor in the error introduced by the change in temperature as we rise.

Barometer pressure sensors can have a height resolution of less than 1 meter, which is significantly better than a GPS system (about 20 meters in height resolution). In the navigation application, the altimeter is used to distinguish between stacked street levels for car navigation and floor level in buildings for pedestrian navigation.

• Flow sensing

This is the use of pressure sensors in conjunction with the venturi effect to measure flow. The differential pressure is measured between two segments of the venturi tube having different aperture. The pressure difference between the two segments is directly proportional to the flow rate through the venturi tube. Low pressure sensors are almost always necessary because of the relatively small pressure differentials.

• Level/depth sensing

Pressure sensors can also be used to calculate fluid levels. This technique is usually used to measure submerged body depths (such as divers or submarine), or level of contents in the tank (as in the water tower). For most practical purposes, the fluid level is proportional to the pressure. In the case of fresh water where the content is under atmospheric pressure, 1psi = 27.7 inH20/1Pa = 9.81 mmH20. The basic equation for such measurements is

${\ displaystyle P = \ rho gh}$

where P = pressure, ? = liquid density, g = standard gravity, h = column fluid height above pressure sensor

• Test leakage

Pressure sensors can be used to feel pressure decay due to system leakage. This is usually done by comparison to known leaks using differential pressure, or by using pressure sensors to measure pressure changes over time.

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Correction ratiometric output transducer

Transduser piezoresistif dikonfigurasi sebagai jembatan Wheatstone sering menunjukkan perilaku ratiometric dengan hormat tidak hanya untuk tekanan diukur, tetapi juga tegangan suplai transduser.

${\ displaystyle V _ {\ mathrm {out}} = {P \ kali K \ kali Vs _ {\ mathrm {actual}} \ over Vs _ {\ mathrm {ideal}}} }  ÂÂ$

Where:

${\ displaystyle V _ {\ mathrm {out}}}  ÂÂ$ adalah tegangan output transduser.

${\ displaystyle P}  ÂÂ$ adalah tekanan terukur yang sebenarnya.

${\ displaystyle K}  ÂÂ$ adalah faktor skala transduser nominal (diberi tegangan suplai transduser yang ideal) dalam satuan tegangan per tekanan.

${\ displaystyle Vs _ {\ mathrm {actual}}}  ÂÂ$ adalah tegangan suplai transduser yang sebenarnya.

${\ displaystyle Vs _ {\ mathrm {ideal}}}  ÂÂ$ adalah tegangan suplai transduser yang ideal.

Mengoreksi pengukuran dari transduser yang menunjukkan perilaku ini memerlukan pengukuran tegangan suplai transduser yang sebenarnya serta tegangan output dan menerapkan transformasi invers dari perilaku ini ke sinyal output:

${\ displaystyle P = {V _ {\ mathrm {out}} \ kali Vs _ {\ mathrm {ideal}} \ over K \ kali Vs _ {\ mathrm {actual}}} }  ÂÂ$

Note: Common mode signals are often present in transducers configured because Wheatstone bridges are not considered in this analysis.

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See also

• Altimeter
• Barometer
• Dynamic pressure
• Sensor list
• MAP sensor
• Pressure

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References

Source of the article : Wikipedia