View source for Schematic

{{Short description|Representation of a system using abstract graphic symbols}}
{{About|technical illustrations||Schema (disambiguation){{!}}Schema|Schematic (Band)||}}
{{more citations needed |date=October 2013}}
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A '''schematic''', or '''schematic diagram''', is a designed representation of the elements of a [[system]] using abstract, graphic [[symbol]]s rather than realistic pictures. A schematic usually omits all details that are not relevant to the key information the schematic is intended to convey, and may include oversimplified elements in order to make this essential meaning easier to grasp, as well as additional organization of the information.

For example, a subway map intended for passengers may represent a subway station with a dot. The dot is not intended to resemble the actual station at all but aims to give the viewer information without unnecessary visual clutter. A schematic diagram of a chemical process uses symbols in place of detailed representations of the vessels, piping, valves, pumps, and other equipment that compose the system, thus emphasizing the functions of the individual elements and the interconnections among them and suppresses their physical details. In an electronic [[circuit diagram]], the layout of the symbols may not look anything like the circuit as it appears in the physical world: instead of representing the way the circuit ''looks'', the schematic aims to capture, on a more general level, the way it ''works''. This may be contrasted with a [[wiring diagram]], which preserves the spatial relationships between each of its components.

==Types==
'''Schematics''' and other types of diagrams, e.g.,
{|style="width:100%"
|style="vertical-align:top; width:25px;"|
|style="vertical-align:top;"|
<gallery mode=packed style="text-align:left">
File:London Underground Overground DLR Crossrail map.svg|[[Transit map]], a schematic map (i.e. not drawn to scale, stations are equidistant, lines are drawn at 45 and 90-degree angles)
File:US 2000 census population density map by state.svg|[[Population density|Population density map]]
File:Automotive diagrams 01 En.png|Schematic of a [[drive train]]
File:Gear pump exploded.svg|[[Exploded view|Exploded-view]] [[engineering drawing]]
</gallery>
<gallery mode="packed" style="text-align:left" class="skin-invert-image">
File:Continuous Binary Fractional Distillation EN.svg|[[Chemical engineering]] schematic
File:4 bit counter.svg|Electrical [[circuit diagram]] for [[Transistor-transistor logic|TTL]] counter, a type of [[state machine]]
</gallery>
|}

A '''semi-schematic''' diagram combines some of the abstraction of a purely schematic diagram with other elements displayed as realistically as possible, for various reasons. It is a compromise between a purely abstract diagram (e.g. the schematic of the Washington Metro) and an exclusively realistic representation (e.g. the corresponding aerial view of Washington).
<gallery widths="220px" heights="165px">
File:Part of Tabula Peutingeriana.jpg|A semi-schematic map: [[Tabula Peutingeriana]]. While roads and features appear as abstract representations without resemblance to reality, their locations, orientations, and distances are as accurate as possible to make the map practical.
</gallery>

==Electrical and electronic industry==
{{Main|Circuit diagram}}
[[File:Circuit diagram – pictorial and schematic.png|right|thumb|Comparison of pictorial and schematic styles of circuit diagrams]]
[[File:Joule_thief_schematic_de.svg|thumb|Example of a [[joule thief]] circuit driving an [[Light-emitting diode|LED]].]]

In electrical and electronic industry, a schematic diagram is often used to describe the design of equipment. Schematic diagrams are often used for the maintenance and repair of electronic and electromechanical systems.<ref name=FV75>Thomas E. French, Charles J. Vierck (1975). ''Engineering Drawing and Graphic Technology, Eleventh Edition''. McGraw Hill. {{ISBN|0-07-022157-X}}.  pp. 621–624.</ref> While schematics were traditionally drawn by hand, using standardized templates or pre-printed adhesive symbols, today [[electronic design automation]] software (EDA or "electrical CAD") is often used.

In electronic design automation, until the 1980s schematics were virtually the only formal representation for circuits. More recently, with the progress of computer technology, other representations were introduced and specialized [[computer language]]s were developed, since with the explosive growth of the complexity of electronic circuits, traditional schematics are becoming less practical. For example, [[hardware description language]]s are indispensable for modern [[digital circuit]] design.

Schematics for electronic circuits are prepared by designers using EDA ([[electronic design automation]]) tools called [[schematic capture]] tools or [[schematic entry]] tools. These tools go beyond simple drawing of devices and connections. Usually they are integrated into the whole design flow and linked to other EDA tools for verification and simulation of the circuit under design.

[[Programmable logic controller]]s (PLC) can be programmed using [[Ladder logic|ladder diagrams]].

In electric power systems design, a schematic drawing called a [[one-line diagram|''one-line'' ''diagram'']] is frequently used to represent [[Electrical substation|substations]], distribution systems or even whole electrical power grids. These diagrams simplify and compress the details that would be repeated on each phase of a [[three-phase]] system, showing only one element instead of three. Electrical diagrams for switchgear often have common device functions designate by [[ANSI Device Numbers|standard function numbers]]. Another type of diagram used for power systems is a ''three-line diagram''.

For analysis purposes of a power system, from the one-line diagram, if the system is balanced, an ''equivalent per-phase'' (or ''single-phase'') ''schematic diagram'' can be obtained. If all of the parameters are represented as impedances and voltage sources, the equivalent per-phase schematic diagram is called an ''impedance diagram''. If all of the parameters are represented as admittances and current sources, the equivalent per-phase schematic diagram is called an ''admittance diagram''.

If the power system is unbalanced, but it is [[Linear system|linear]] (or can be approximated by a linear system), then Fortescue's theorem ([[symmetrical components]]) can be applied. In this way, from the one-line diagram, three different per-phase schematic diagrams are obtained, known as ''sequence diagrams'': ''positive sequence diagram'', ''negative sequence diagram'', and ''zero sequence diagram''. Each of these diagrams can be represented as an impedance diagram or as an admittance diagram.

==Schematics in repair manuals==

Schematic diagrams are used extensively in repair manuals to help users understand the interconnections of parts, and to provide graphical instruction to assist in dismantling and rebuilding mechanical assemblies.  Many automotive and motorcycle [[Repairing|repair]] manuals devote a significant number of pages to schematic diagrams.

==See also==
{{Portal|Electronics}}
{{Wiktionary}}
{{Commons category}}
* [[Energy systems language]]
* [[Chart]]
* [[Diagram]]
* {{slink|Logic gate#Symbols}}
* [[Straight-line diagram]]
* [[Topological map]]
* [[Transit map]]
* [[Open-source hardware]]

==References==
{{Reflist|30em}}

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[[Category:Diagrams]]
[[Category:Electronic design automation]]
[[Category:Technical communication]]
[[Category:Infographics]]