Antiunitary operator: Difference between revisions

From formulasearchengine
Jump to navigation Jump to search
en>Stevvers
m verb -> adjective
 
Line 1: Line 1:
{{Use mdy dates|date=September 2013}}
<!-- [[Image:Piezoelectric_quartz.png|thumb|Quartz: When a force is applied to the tetrahedon a displacement of the [[cation]] charge towards the center of the [[anion]] charges occurs]] -->
[[Image:SchemaPiezo.gif|thumb|A piezoelectric disk generates a voltage when deformed (change in shape is greatly exaggerated)]]


A '''piezoelectric sensor''' is a device that uses the [[piezoelectric effect]], to measure changes in [[pressure]], [[acceleration]], [[Strain (materials science)|strain]] or [[force]] by converting them to an [[electricity|electrical]] charge.  The prefix ''piezo-'' is Greek for 'press' or 'squeeze'.


==Applications==
If you want to do something creative, consider ways to create viral videos. Brainstorm ideas that you think are rip riotously hilarious, then start putting them into action. Post them on YouTube, turn on ads and, if they work, watch the money start rolling in! Learn about marketing to see how you can get them even more popular. [http://www.comoganhardinheiro101.com/?p=66 como ganhar dinheiro pela internet] If you know how to prepare taxes, you can earn money online. Apply for the necessary government licenses and then begin offering your services online. Many of today's top producers work from home with only their laptop and an email address. For best results, continually advertise your services throughout the year. <br><br><br>Manage your time wisely when you are trying to make money online. You may have a real-world job, which means you have to budget time wisely. Set a schedule that will allow you enough time to balance the two. Also make sure that you are being efficient in that time, so you don't run into stress [http://www.comoganhardinheiro101.com/category/opcoes-binarias/ como ganhar dinheiro na internet] about working online. Becoming a ghost writer is a great way to earn money online. There are people who need content for their websites, but who lack good writing skills. You can write for them and earn money for what you write. Many people are earning a good income writing for others this way.<br><br>Affiliate marketing can be a good way to earn money online if you have a lot of time and energy to spend on website setup and promotion. Affiliate marketers market the products of others in a number of ways. You can create a website and promote [http://www.comoganhardinheiro101.com/ferramentas/ como ganhar dinheiro na internet] it. Creating a blog or posting on the blogs of others in your niche is also an excellent way to share product information. Making smart use of social media and e mail marketing are also possibilities for successful affiliate marketing.<br><br>As you can see from the above article, it is easy to understand how to make money online when you get the knowledge through great tips. You can join the millions of people worldwide who make money each day, if you [http://www.comoganhardinheiro101.com/?p=16 ganhar dinheiro na internet] pay close attention to the tips that you have just read. Making money online is a skill, and if you continue to study good tips and ideas such as these, there is no reason why you cannot make lots of money online.<br><br>Many sites require a payment for information that they claim will allow you to make a lot of money online. A good rule of thumb is to never pay anything to get that type of information.  For more information regarding [http://ganhedinheironainternet.comoganhardinheiro101.com como ganhar dinheiro] look at ganhedinheironainternet.comoganhardinheiro101.com Legitimate sites may ask you to qualify by taking a test, but they will not require any type of payment. [http://www.comoganhardinheiro101.com/ferramentas/ como conseguir dinheiro] People love handmade goods. They are very trendy right now, so if you are artsy, go make some money! So, if you are the creative type, whether it's sewing, knitting or any other craft work, now is the time to produce your goods. Both Etsy and eBay could be generating an income for you.<br><br>that's a lie. Don't fall prey to these types of websites and always read the reviews before joining. Talking to experts in their field can help you to use [http://www.comoganhardinheiro101.com/tag/ganhar-dinheiro/ ganhar dinheiro pela internet] the Internet successfully. Try to network with people who do what you want to do. Doing these things can help give you an advantage over your competition. <br><br><br>Do you have a heart for customer service? If so, you can make money online answering phone calls for businesses. Additionally, you can make money by chatting online with a business's customer to help them solve problems and answer their questions. There are many customer service sites available including: LiveOps, Working Solutions [http://www.comoganhardinheiro101.com/ ganhe dinheiro na internet] and ACD Direct. Write online to make money. There are quite a few legitimate companies that pay people to write articles online. You can find many different companies that will pay you to write different content with varying topics. If you enjoy writing, you should do research to look for companies that will pay you to write online.<br><br>If you want to do something creative, consider ways to create viral videos. Brainstorm ideas that you think are rip riotously hilarious, then start putting them into action. Post them on YouTube, turn on ads and, if they work, watch the money start rolling in! Learn about marketing to see how you can get them even more popular. [http://www.comoganhardinheiro101.com/homebox/ como conseguir dinheiro] If you know how to prepare taxes, you can earn money online. Apply for the necessary government licenses and then begin offering your services online. Many of today's top producers work from home with only their laptop and an email address. For best results, continually advertise your services throughout the year.<br><br>
[[Image:Piezoelectric pickup1.jpg|thumb|Piezoelectric disk used as a [[guitar pickup]]]]
Piezoelectric sensors have proven to be versatile tools for the measurement of various processes. They are used for [[quality assurance]], [[process control]] and for research and development in many industries. Although the piezoelectric effect was discovered by [[Pierre Curie]] in 1880, it was only in the 1950s that the piezoelectric effect started to be used for industrial sensing applications. Since then, this measuring principle has been increasingly used and can be regarded as a [[mature technology]] with an outstanding inherent reliability. It has been successfully used in various applications, such as in [[medical]], [[aerospace]], [[Nuclear engineering|nuclear]] instrumentation, and as a pressure sensor in the touch pads of mobile phones. In the [[automotive industry]], piezoelectric elements are used to monitor combustion when developing [[internal combustion engines]]. The sensors are either directly mounted into additional holes into the cylinder head or the spark/glow plug is equipped with a built in miniature piezoelectric sensor.[http://www.avl.com/wo/webobsession.servlet.go/encoded/YXBwPWJjbXMmcGFnZT12aWV3JiZub2RlaWQ9NDAwMDU1MjUy.html]


The rise of piezoelectric technology is directly related to a set of inherent advantages. The high [[modulus of elasticity]] of many piezoelectric materials is comparable to that of many metals and goes up to {{nowrap|10<sup>6</sup> N/m²}} {{citation needed|date=June 2012}}. Even though piezoelectric sensors are electromechanical systems that react to [[compression (physical)|compression]], the sensing elements show almost zero deflection. This is the reason why piezoelectric sensors are so rugged, have an extremely high natural frequency and an excellent linearity over a wide [[amplitude]] range. Additionally, piezoelectric technology is insensitive to [[electromagnetic field]]s and [[radiation]], enabling measurements under harsh conditions. Some materials used (especially [[gallium phosphate]] [http://www.piezocryst.com] or [[tourmaline]]) have an extreme stability even at high temperature, enabling sensors to have a working range of up to {{nowrap|1000 °C}}. Tourmaline shows [[pyroelectricity]] in addition to the piezoelectric effect; this is the ability to generate an electrical signal when the temperature of the crystal changes. This effect is also common to [[piezoceramic]] materials. Gautschi in ''Piezoelectric Sensorics'' (2002) offers this comparison table of characteristics of piezo sensor materials vs other types:<ref>{{cite book
Don't buy every book about making money online. Most of the time, these books are sold by people whose claim to fame is that they are teaching people how to make money [http://www.comoganhardinheiro101.com/ferramentas/ como conseguir dinheiro] como ficar rico online. Before you buy an e-book or book about making money, make sure that you know a little about the author, and that you have seen  como ficar rico testimonials about the book.<br><br>Many sites require a payment for information that they claim will allow you to make a lot of money online. A good rule of thumb is to never pay anything to get that type of information. Legitimate sites may ask you to qualify by taking a test, but they will not require any type of payment. [http://www.comoganhardinheiro101.com/?p=16 como ganhar dinheiro na internet] People love handmade goods. They are very trendy right now, so if you are artsy, go make some money! So, if you are the creative type, whether it's sewing, knitting or any other craft work, now is the time to produce your goods. Both Etsy and eBay could be generating an income for you.<br><br>As you can see from the above article, it is easy to understand how to make money online when you get the [http://ganhardinheiro.comoganhardinheiro101.com/ knowledge] through great tips. You can join the millions of people worldwide who make money each day, if you [http://www.comoganhardinheiro101.com/?p=12 como ficar rico] pay close attention to the tips that you have just read. Making money online is a skill, and if you continue to study good tips and ideas such as these, there is no reason why you cannot make lots of money online.<br><br>Several websites out there pay for people to do tasks that cannot be handled by a computer. It might be flagging inappropriate activity or finding the name of a business on a receipt. These tasks require human intelligence to find the answer. They are reasonably simple to perform and can provide you with some extra [http://www.comoganhardinheiro101.com/?p=66 ganhar dinheiro na internet] money. Translate documents if you are fluent in a second language and want to make money on the side. Check out the freelancing sites to find people who will need things altered into a different language. This can be anyone from a large corporation to an individual who wants to translate something for a friend.
| last = Gautschi
| first = G.
| title = Piezoelectric sensorics
| year = 2002
| page=3
| publisher = Springer Berlin, Heidelberg, New York
| url=http://books.google.com/books?id=-nYFSLcmc-cC&pg=PA3#v=onepage&q&f=false
| via=Google Books
}}</ref>
{| class="wikitable"
|-
! Principle
! Strain<br/>Sensitivity [V/µε]
! Threshold<br/>[µε]
! Span to<br/>threshold ratio
|-
|Piezoelectric
| 5.0
| 0.00001
| 100,000,000
|-
|Piezoresistive
| 0.0001
| 0.0001
| 2,500,000
|-
|Inductive
| 0.001
| 0.0005
| 2,000,000
|-
|Capacitive
| 0.005
| 0.0001
| 750,000
|-
|Resistive
| 0.000005
| 0.01
| 50,000
|}
 
One disadvantage of piezoelectric sensors is that they cannot be used for truly static measurements. A static force will result in a fixed amount of charges on the piezoelectric material. While working with conventional readout electronics, imperfect insulating materials, and reduction in internal sensor [[Electrical resistance|resistance]] will result in a constant loss of [[electron]]s, and yield a decreasing signal. Elevated temperatures cause an additional drop in [[internal resistance]] and sensitivity. The main effect on the piezoelectric effect is that with increasing pressure loads and temperature, the sensitivity is reduced due to twin-formation. While [[quartz]] sensors need to be cooled during measurements at temperatures above {{nowrap|300 °C}}, special types of crystals like GaPO4 [[gallium phosphate]] do not show any twin formation up to the melting point of the material itself.
 
However, it is not true that piezoelectric sensors can only be used for very fast processes or at ambient conditions. In fact, there are numerous applications that show quasi-static measurements, while there are other applications with temperatures higher than {{nowrap|500 °C}}.
 
Piezoelectric sensors can also be used to determine aromas in the air through measurements of resonance and capacitance simultaneously. Computer controlled electronics vastly increase the range of potential applications for piezoelectric sensors.<ref name=PROCHE245>{{cite journal|last=Wali|first=R Paul|title=An electronic nose to differentiate aromatic flowers using a real-time information-rich piezoelectric resonance measurement|journal=Procedia Chemistry |date=October 2012 |pages=194–202 |doi=10.1016/j.proche.2012.10.146}}</ref>
 
Piezoelectric sensors are also seen in nature. The collagen in [[bone]] is piezoelectric, and is thought by some to act as a biological force sensor.<ref>{{cite web|last=Lakes |first=Roderic |date=July 8, 2013 |url=http://silver.neep.wisc.edu/~lakes/BoneElectr.html |title=Electrical Properties of Bone - a review |publisher=University of Wisconsin |accessdate=September 1, 2013}}</ref><ref>{{cite web|url=http://www.ortho.lsuhsc.edu/Faculty/Marino/EL/EL4/Piezo.html |title=Piezoelectricity |last=Becker |first=Robert O. |last2=Marino |first2=Andrew A. |publisher=Department of Orthopaedic Surgery at Louisiana State University Health Sciences Center |archiveurl=http://web.archive.org/web/20090802194455/http://www.ortho.lsuhsc.edu/Faculty/Marino/EL/EL4/Piezo.html |archivedate=August 2, 2009 |accessdate=September 1, 2013}}</ref>
 
==Principle of operation==
Depending on how a piezoelectric material is cut, three main modes of operation can be distinguished: transverse, longitudinal, and shear.
 
;'''Transverse effect''':A force is applied along a neutral axis (y) and the charges are generated along the (x) direction, perpendicular to the line of force. The amount of charge depends on the geometrical dimensions of the respective piezoelectric element. When dimensions <math>a, b, c</math> apply,
::<math>C_x= d_{xy} F_y b/a~</math>,
:where <math>a</math> is the dimension in line with the neutral axis, <math>b</math> is in line with the charge generating axis and <math>d</math> is the corresponding piezoelectric coefficient.[http://www.piezo.com/tech1terms.html#d]
 
;'''Longitudinal effect''':The amount of charge produced is strictly proportional to the applied force and is independent of size and shape of the piezoelectric element. Using several elements that are mechanically in series and electrically in [[series and parallel circuits|parallel]] is the only way to increase the charge output. The resulting charge is
::<math> C_x=d_{xx}  F_x  n~</math>,
:where  <math>d_{xx}</math> is the piezoelectric coefficient for a charge in x-direction released by forces applied along x-direction (in [[coulomb|pC]]/[[Newton (unit)|N]]). <math>F_x</math> is the applied Force in x-direction [N] and <math>n</math> corresponds to the number of stacked elements .
 
force applied and the element dimension.
 
==Electrical properties==
 
[[Image:Piezoelectric sensor electrical model.svg|thumb|Schematic symbol and electronic model of a piezoelectric sensor]]
 
A piezoelectric transducer has very high DC [[output impedance]] and can be modeled as a proportional [[voltage source]] and [[Electronic filter|filter network]].  The voltage ''V'' at the source is directly proportional to the applied force, pressure, or strain.<ref name="interfacing">{{Cite web
| title = Interfacing Piezo Film to Electronics
| work = Measurement Specialties
| accessdate = December 2, 2007
|date=March 2006
| url = http://metrolog.net/files/tech/meas_spec/piezo_an/piezofilm_interface_electronics_enus_metrolog.pdf
|format=PDF}}</ref>  The output signal is then related to this mechanical force as if it had passed through the equivalent circuit.
 
[[Image:Piezoelectric sensor frequency response.svg|thumb|Frequency response of a piezoelectric sensor; output voltage vs applied force]]
 
A detailed model includes the effects of the sensor's mechanical construction and other non-idealities.<ref name="novel">{{Cite paper
| publisher = Universitat Politècnica de Catalunya
| pages = 242
| last = Alfredo Vázquez Carazo
| title = Novel Piezoelectric Transducers for High Voltage Measurements
| year = 2000
| month = January
}}</ref>  The inductance ''L''<sub>m</sub> is due to the seismic [[mass]] and [[inertia]] of the sensor itself.  ''C''<sub>e</sub> is inversely proportional to the mechanical [[Elasticity (physics)|elasticity]] of the sensor.  ''C''<sub>0</sub> represents the static capacitance of the transducer, resulting from an inertial mass of infinite size.<ref name="novel"/><!--I don't understand this one-->  ''R''<sub>i</sub> is the insulation [[Leakage (electronics)|leakage resistance]] of the transducer element. If the sensor is connected to a [[load resistance]], this also acts in parallel with the insulation resistance, both increasing the high-pass cutoff frequency.
 
[[Image:Piezoelectric sensor simplified electrical models.svg|thumb|In the flat region, the sensor can be modeled as a voltage source in series with the sensor's capacitance or a charge source in parallel with the capacitance]]
 
For use as a sensor, the flat region of the frequency response plot is typically used, between the high-pass cutoff and the resonant peak.  The load and leakage resistance need to be large enough that low frequencies of interest are not lost. A simplified equivalent circuit model can be used in this region, in which ''C''<sub>s</sub> <!-- equal to C0+Ce according to the novel thesis? --> represents the capacitance of the sensor surface itself, determined by the standard [[Capacitance#Capacitors|formula for capacitance of parallel plates]].<ref name="novel"/><ref>{{cite web
| publisher = Texas Instruments
| last = Karki
| first = James
| title = Signal Conditioning Piezoelectric Sensors
| accessdate = December 2, 2007
|date=September 2000
| url = http://focus.ti.com/lit/an/sloa033a/sloa033a.pdf
|format=PDF}}</ref>  It can also be modeled as a charge source in parallel with the source capacitance, with the charge directly proportional to the applied force, as above.<ref name="interfacing"/>
 
==Sensor design==
 
[[Image:Electronic component piezo.jpg|thumb|Metal disks with piezo material, used in buzzers or as [[contact microphone]]s]]
 
Based on piezoelectric technology various physical quantities can be measured; the most common are pressure and acceleration. <!--The figure below shows schematic configurations of those sensors in the transverse configuration. In both designs, the elements are thin cuboids that are loaded along their longest extension. -->For pressure sensors, a thin [[artificial membrane|membrane]] and a massive base is used, ensuring that an applied pressure specifically loads the elements in one direction. For [[accelerometer]]s, a [[seismic mass]] is attached to the crystal elements. When the accelerometer experiences a motion, the invariant seismic mass loads the elements according to Newton’s second law of motion <math>F=m a</math>.
 
The main difference in the working principle between these two cases is the way forces are applied to the sensing elements. In a pressure sensor a thin membrane is used to transfer the force to the elements, while in accelerometers the forces are applied by an attached seismic mass.
 
Sensors often tend to be sensitive to more than one physical quantity. Pressure sensors show false signal when they are exposed to vibrations. Sophisticated pressure sensors therefore use acceleration compensation elements in addition to the pressure sensing elements. By carefully matching those elements, the acceleration signal (released from the compensation element) is subtracted from the combined signal of pressure and acceleration to derive the true pressure information.
 
Vibration sensors can also be used to harvest otherwise wasted energy from mechanical vibrations. This is accomplished by using piezoelectric materials to convert mechanical strain into usable electrical energy.<ref>{{cite web
| publisher = Mide Technology
| last = Ludlow
| first = Chris
| title = Energy Harvesting with Piezoelectric Sensors
| accessdate = May 21, 2008
|date=May 2008
| url = http://www.mide.com/pdfs/vibration_harvesting_conference_2008.pdf
|format=PDF}}</ref>
 
==Sensing materials==
Two main groups of materials are used for piezoelectric sensors: piezoelectric ceramics and single crystal materials.
The ceramic materials (such as [[PZT]] ceramic) have a piezoelectric constant / sensitivity that is roughly two [[order of magnitude|orders of magnitude]] higher than those of the natural single crystal materials and can be produced by inexpensive [[sintering]] processes. The piezoeffect in piezoceramics is "trained", so their high sensitivity degrades over time. This degradation is highly correlated with increased temperature.
The less sensitive natural single crystal materials ([[gallium phosphate]], [[quartz]], [[tourmaline]]) have a higher – when carefully handled, almost unlimited – long term stability.  There are also new single crystal materials commercially available such as Lead Magnesium Niobate-Lead Titanate (PMN-PT).  These materials offer improved sensitivity over  [[PZT]] but have a lower maximum [[operating temperature]] and are currently more expensive to manufacture.{{citation needed|date=August 2013}}
 
==See also==
* [[Charge amplifier]]
* [[List of sensors]]
* [[Piezoelectricity]]
* [[Piezoresistive effect]]
 
==References==
<references/>
 
==External links==
*Material constants of [http://www.piezocryst.com/gapo4_down.php gallium phosphate]
*[http://www.newpiezo.com/sensors.html Langatate] - new material for high-temperature piezoelectric sensors
*Spark-Plug with integrated miniaturized piezoelectric pressure sensor [http://www.avl.com/wo/webobsession.servlet.go/encoded/YXBwPWJjbXMmcGFnZT12aWV3JiZub2RlaWQ9NDAwMDU1MjUy.html]
*[http://www.pcb.com/techsupport/tech_gen.php Using the Piezoelectric Effect in Sensors] {{dead link|date=April 2013}}
 
{{DEFAULTSORT:Piezoelectric Sensor}}
[[Category:Sensors]]

Latest revision as of 14:42, 21 November 2014


If you want to do something creative, consider ways to create viral videos. Brainstorm ideas that you think are rip riotously hilarious, then start putting them into action. Post them on YouTube, turn on ads and, if they work, watch the money start rolling in! Learn about marketing to see how you can get them even more popular. como ganhar dinheiro pela internet If you know how to prepare taxes, you can earn money online. Apply for the necessary government licenses and then begin offering your services online. Many of today's top producers work from home with only their laptop and an email address. For best results, continually advertise your services throughout the year. 


Manage your time wisely when you are trying to make money online. You may have a real-world job, which means you have to budget time wisely. Set a schedule that will allow you enough time to balance the two. Also make sure that you are being efficient in that time, so you don't run into stress como ganhar dinheiro na internet about working online. Becoming a ghost writer is a great way to earn money online. There are people who need content for their websites, but who lack good writing skills. You can write for them and earn money for what you write. Many people are earning a good income writing for others this way.

Affiliate marketing can be a good way to earn money online if you have a lot of time and energy to spend on website setup and promotion. Affiliate marketers market the products of others in a number of ways. You can create a website and promote como ganhar dinheiro na internet it. Creating a blog or posting on the blogs of others in your niche is also an excellent way to share product information. Making smart use of social media and e mail marketing are also possibilities for successful affiliate marketing.

As you can see from the above article, it is easy to understand how to make money online when you get the knowledge through great tips. You can join the millions of people worldwide who make money each day, if you ganhar dinheiro na internet pay close attention to the tips that you have just read. Making money online is a skill, and if you continue to study good tips and ideas such as these, there is no reason why you cannot make lots of money online.

Many sites require a payment for information that they claim will allow you to make a lot of money online. A good rule of thumb is to never pay anything to get that type of information. For more information regarding como ganhar dinheiro look at ganhedinheironainternet.comoganhardinheiro101.com Legitimate sites may ask you to qualify by taking a test, but they will not require any type of payment. como conseguir dinheiro People love handmade goods. They are very trendy right now, so if you are artsy, go make some money! So, if you are the creative type, whether it's sewing, knitting or any other craft work, now is the time to produce your goods. Both Etsy and eBay could be generating an income for you.

that's a lie. Don't fall prey to these types of websites and always read the reviews before joining. Talking to experts in their field can help you to use ganhar dinheiro pela internet the Internet successfully. Try to network with people who do what you want to do. Doing these things can help give you an advantage over your competition.


Do you have a heart for customer service? If so, you can make money online answering phone calls for businesses. Additionally, you can make money by chatting online with a business's customer to help them solve problems and answer their questions. There are many customer service sites available including: LiveOps, Working Solutions ganhe dinheiro na internet and ACD Direct. Write online to make money. There are quite a few legitimate companies that pay people to write articles online. You can find many different companies that will pay you to write different content with varying topics. If you enjoy writing, you should do research to look for companies that will pay you to write online.

If you want to do something creative, consider ways to create viral videos. Brainstorm ideas that you think are rip riotously hilarious, then start putting them into action. Post them on YouTube, turn on ads and, if they work, watch the money start rolling in! Learn about marketing to see how you can get them even more popular. como conseguir dinheiro If you know how to prepare taxes, you can earn money online. Apply for the necessary government licenses and then begin offering your services online. Many of today's top producers work from home with only their laptop and an email address. For best results, continually advertise your services throughout the year.

Don't buy every book about making money online. Most of the time, these books are sold by people whose claim to fame is that they are teaching people how to make money como conseguir dinheiro como ficar rico online. Before you buy an e-book or book about making money, make sure that you know a little about the author, and that you have seen como ficar rico testimonials about the book.

Many sites require a payment for information that they claim will allow you to make a lot of money online. A good rule of thumb is to never pay anything to get that type of information. Legitimate sites may ask you to qualify by taking a test, but they will not require any type of payment. como ganhar dinheiro na internet People love handmade goods. They are very trendy right now, so if you are artsy, go make some money! So, if you are the creative type, whether it's sewing, knitting or any other craft work, now is the time to produce your goods. Both Etsy and eBay could be generating an income for you.

As you can see from the above article, it is easy to understand how to make money online when you get the knowledge through great tips. You can join the millions of people worldwide who make money each day, if you como ficar rico pay close attention to the tips that you have just read. Making money online is a skill, and if you continue to study good tips and ideas such as these, there is no reason why you cannot make lots of money online.

Several websites out there pay for people to do tasks that cannot be handled by a computer. It might be flagging inappropriate activity or finding the name of a business on a receipt. These tasks require human intelligence to find the answer. They are reasonably simple to perform and can provide you with some extra ganhar dinheiro na internet money. Translate documents if you are fluent in a second language and want to make money on the side. Check out the freelancing sites to find people who will need things altered into a different language. This can be anyone from a large corporation to an individual who wants to translate something for a friend.