A feedthrough is a

conductor Conductor or conduction may refer to: Biology and medicine * Bone conduction, the conduction of sound to the inner ear * Conduction aphasia, a language disorder Mathematics * Conductor (ring theory) * Conductor of an abelian variety * Cond ...

used to carry a signal through an enclosure or printed

circuit board A printed circuit board (PCB), also called printed wiring board (PWB), is a laminated sandwich structure of conductive and insulating layers, each with a pattern of traces, planes and other features (similar to wires on a flat surface) ...

. Like any conductor, it has a small amount of

capacitance Capacitance is the ability of an object to store electric charge. It is measured by the change in charge in response to a difference in electric potential, expressed as the ratio of those quantities. Commonly recognized are two closely related ...

. A "feedthrough capacitor" has a guaranteed minimum value of built in it and is used for bypass purposes in ultra-high-frequency applications. 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 A thermocouple, also known as a "thermoelectrical thermometer", is an electrical device consisting of two dissimilar electrical conductors forming an electrical junction. A thermocouple produces a temperature-dependent voltage as a result of the ...

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 RF or

microwave Microwave is a form of electromagnetic radiation with wavelengths shorter than other radio waves but longer than infrared waves. Its wavelength ranges from about one meter to one millimeter, corresponding to frequency, frequencies between 300&n ...

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 An electron microscope is a microscope that uses a beam of electrons as a source of illumination. It uses electron optics that are analogous to the glass lenses of an optical light microscope to control the electron beam, for instance focusing it ...

s, require electrical connections through the

pressure vessel A pressure vessel is a container designed to hold gases or liquids at a pressure substantially different from the ambient pressure. Construction methods and materials may be chosen to suit the pressure application, and will depend on the size o ...

. 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 A spark plug (sometimes, in British English, a sparking plug, and, colloquially, a plug) is a device for delivering electric current from an ignition system to the combustion chamber of a spark-ignition engine to ignite the compressed fuel/air ...

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 A spark gap consists of an arrangement of two Conductor (material), conducting electrodes separated by a gap usually filled with a gas such as air, designed to allow an electric spark to pass between the conductors. When the potential differenc ...

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.

References

{{Reflist Electrical components de:Leistungstransformator#Durchf.C3.BChrungen

See also

References