View source for Feedthrough

{{Redirect-distinguish|Feedthrough capacitor|DC block}}
{{For|the interconnect in printed circuit boards|via (electronics)}}
[[File:60kV Feedthrough.jpg|thumb|60 kV vacuum feedthrough on a [[Vacuum flange#CF (Conflat)|conflat flange]]]]
[[File:Feedtrough cap small.jpg|thumb|Ceramic feedthrough capacitor with [[cable lug]] and a capacitance of 1&nbsp;nF.]]

A '''feedthrough''' is a [[Conductor (material)|conductor]] used to carry a signal through an enclosure or printed [[circuit board]]. Like any conductor, it has a small amount of [[capacitance]].  {{anchor|Feedthrough capacitor}}A "feedthrough capacitor" has a guaranteed minimum value of {{clarify span|text=shunt capacitance|date=August 2020}} built in it and is used for bypass purposes in ultra-high-frequency applications.<ref>{{Cite web|url=http://encyclopedia2.thefreedictionary.com/feedthrough+capacitor|title = Feedthrough capacitor}}</ref> Feedthroughs can be divided into power and instrumentation categories. Power feedthroughs are used to carry either high current or high voltage. Instrumentation feedthroughs are used to carry electrical signals (including [[thermocouple]]s) which are normally low current or voltage. Another special type is what is commonly known as RF-feedthrough, specifically designed to carry very high frequency [[Radio frequency|RF]] or [[microwave]] electrical signals.

A feedthrough electrical connection may have to withstand considerable pressure difference across its length. Systems that operate under high vacuum, such as [[electron microscope]]s, require electrical connections through the [[pressure vessel]]. Similarly, submersible vehicles require feedthrough connections between exterior instruments and devices and the controls within the vehicle pressure hull. A very common example of a feedthrough connection is an automobile [[spark plug]] where the body of the plug must resist the pressure and temperature produced in the engine, while providing a reliable electrical connection to the [[spark gap]] in the combustion chamber. (Spark plugs are occasionally used as low-cost or improvised feedthrough connections in non-engine applications.)

There are electrical hermetically sealed feedthroughs for instrumentation, high amperage and voltage, coaxial, thermocouple and fiber optics.  Rotary or mechanical feedthroughs also exist. 

==See also==
*[[Vacuum technology]]

==References==
{{Reflist}}

[[Category:Electrical components]]

[[de:Leistungstransformator#Durchf.C3.BChrungen]]