“Force-sensing capacitor”的意思、由来-开放百科全书

A force-sensing capacitor is a material whose capacitance changes when a force, pressure or mechanical stress is applied. They are also known as "force-sensitive capacitors". They can provide improved sensitivity and repeatability compared to force-sensitive resistors^[1] but traditionally required more complicated electronics.^[2]

Operation principle

Typical force sensitive capacitors are examples of parallel plate capacitors. For small deflections, there is a linear relationship between applied force and change in capacitance, which can be shown as follows:

The capacitance,

, equals

, where

is permeability,

is the area of the sensor and

is the distance between parallel plates. If the material is linearly elastic (so follows Hooks Law), then the displacement, due to an applied force

, is

, where

is the spring constant. Combining these equations gives the capacitance after an applied force as:

Assuming that

, which is true for small deformations where

, we can simplify this to:

Production

SingleTact makes force-sensitive capacitors using moulded silicon between two layers of polymide to construct a 0.35{{nbsp}}mm thick sensor, with force ranges from 1{{nbsp}}N to 450{{nbsp}}N.^[3] The 8mm SingleTact has a nominal capacitance of 75{{nbsp}}pF, which increases by 2.2{{nbsp}}pF when the rated force is applied.^[3]

Uses

Force-sensing capacitors can be used to create low-profile force-sensitive buttons. They have been used in medical imaging to map pressures in the esophagus^[4]^[5]and to image breast^[6]^[7] and prostrate cancer.^[8]

References

1. ^{{Cite journal|last=Martinelli|first=L|last2=Hurschler|first2=C|last3=Rosenbaum|first3=D|date=2006-06-01|title=Comparison of Capacitive versus Resistive Joint Contact Stress Sensors|url=http://content.wkhealth.com/linkback/openurl?sid=WKPTLP:landingpage&an=00003086-200606000-00036|journal=Clinical Orthopaedics and Related Research|volume=447|pages=214–220|doi=10.1097/01.blo.0000218730.59838.6a|issn=0009-921X|via=}}
2. ^{{Cite book|url=https://www.worldcat.org/oclc/30781109|title=Principles of measurement systems|last=1943-|first=Bentley, John P.,|date=1995|publisher=Longman Scientific & Technical|isbn=0470234458|edition=3rd|location=Harlow [England]|oclc=30781109}}
3. ^¹{{Cite web|url=https://www.singletact.com/SingleTact_Datasheet.pdf|title=SingleTact Datasheet|last=|first=|date=|website=SingleTact|archive-url=|archive-date=|dead-url=|access-date=}}
4. ^{{cite patent|country=US|number=US10961981|title=High resolution solid state pressure sensor|status=Grant|pubdate=2015-07-14|gdate=|invent1=Pakrs|inventor1-first=Thomas|assign1=Sierra Scientific Instruments Inc}}
5. ^{{Cite news|url=https://www.mdtmag.com/article/2016/03/using-capacitive-force-sensors-next-gen-medical-products|title=Using Capacitive Force Sensors in Next-Gen Medical Products|date=2016-03-01|work=Medical Design Technology|access-date=2018-06-21|language=en}}
6. ^{{Cite journal|last=Egorov|first=V.|last2=Sarvazyan|first2=A.P.|date=2008-09-01|title=Mechanical Imaging of the Breast|url=http://ieeexplore.ieee.org/document/4577635/|journal=IEEE Transactions on Medical Imaging|language=en-US|volume=27|issue=9|pages=1275–1287|doi=10.1109/tmi.2008.922192|issn=0278-0062|pmc=2581459|pmid=18753043|via=}}
7. ^{{Cite web|url=http://suretouch.us/|title=SureTouch|last=|first=|date=|website=SureTouch|language=en-US|archive-url=|archive-date=|dead-url=|access-date=2018-06-21}}
8. ^{{Cite web|url=http://www.artannlabs.com/|title=Artann Labs|last=|first=|date=|website=www.artannlabs.com|language=en-US|archive-url=|archive-date=|dead-url=|access-date=2018-06-21}}