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I have been trying to understand what the term "schematic capture" means, what it involves and what it doesn't involve.

Does it mean being capable of understanding or perhaps drawing some complex electronic circuits expressed in a schematic? There doesn't seem to be a simple clear answer available on the web.

Can someone perhaps explain to me what does this term exactly means, and perhaps give me some examples?

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    \$\begingroup\$ To be perfectly blunt, schematic capture is jargon. It just refers to specialized EE CAD software that lets you draw a schematic. Or it can also refer to the act of drawing the schematic using such software. OrCAD, Altium schematic editor, KiCAD, Eagle, etc all are or contain schematic capture software. Usage examples: "What are you guys using for schematic capture?" "Right now we are at the schematic capture stage, but layout is scheduled to begin next week." "In my last job I was responsible for schematic capture, component selection, supervising layout, and board bring-up" Etc. \$\endgroup\$ – mkeith Jul 21 at 0:43
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    \$\begingroup\$ That is the real answer, @mkeith: it's just jargon that means "drawing/designing the schematic in software". Why did you post it as a comment instead of as an answer? :-) \$\endgroup\$ – Cody Gray Jul 21 at 23:43
  • \$\begingroup\$ @CodyGray too many answers already, some of which I agree with 100%. \$\endgroup\$ – mkeith Jul 22 at 0:25
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In the old days schematics were created with plastic or stainless steel templates and writing instruments on paper or vellum. Photo from Amazon.ca:

enter image description here

Then, in order to use a fancy computer aided design process, the schematic would be "captured" into the digital domain. Often by another person.

You can think of it in the same way as "dialing" your smartphone. Image from Wikipedia:

enter image description here

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To me, Schematic Capture means entering the schematic into a computer program so that the program can extract information from the schematic to be used by the program or by another program.

One example would be to produce a netlist (list of all components and connections on the schematic) that can be passed to a PC board layout program, so that the programs can ensure that the PC board properly implements the circuit shown by the schematic.

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    \$\begingroup\$ Yes, this is the correct meaning. However, it is unclear how the schematic would ever not be entered into a computer program, as that's how schematics are designed now from the very beginning (by inputting them into a computer program), and that has been true for many, many years now. \$\endgroup\$ – Cody Gray Jul 20 at 4:12
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    \$\begingroup\$ I think I would generally start a design using pencil sketches on paper, and only go to the computer when I had a good idea of what I wanted. \$\endgroup\$ – Peter Bennett Jul 20 at 4:34
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    \$\begingroup\$ @CodyGray But that was not true when the term was coined. Instead, progressively-better schematic capture programs became useable for design. It's the same way we still talk about a "word processor", even though the WYSIWYG principle means they now also include desktop publishing capabilities which would previously have been a separate process. Also if you think it's truly unclear, you haven't spent much time with electronic engineers working out details in notepads or on whiteboards. :) \$\endgroup\$ – Graham Jul 20 at 12:10
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    \$\begingroup\$ @CodyGray Not always. I tend to design my embedded systems either as a pin assignment file in a C/C++ program or for bigger projects as a pen/pencil sketch in a notebook. The process of creating a schematic in a CAD software is too slow to aid my thinking and has too many irrelevant steps that interrupts my thought process. Only once I have a good idea of what I want to do (and by this time I usually have lots of paper sketches) do I open a CAD program and slowly transfer my design to software \$\endgroup\$ – slebetman Jul 20 at 14:36
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    \$\begingroup\$ @CodyGray schematic capture means drawing the schematic using software that will allow you to progress to simulation or board layout or both. Drawing a schematic on paper or using graphics software that doesn't know what a schematic is (e.g., MS paint) is not schematic capture. Schematic capture, therefore, can be the same thing as drawing a schematic, if you are drawing the schematic using OrCAD or Altium or Eagle or KiCAD or what have you. But in some cases you can draw a schematic without it being "captured." \$\endgroup\$ – mkeith Jul 21 at 0:40
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It generally just means "Inputted circuit diagram"

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    \$\begingroup\$ This is the answer. It just means capturing the schematic in software form. \$\endgroup\$ – DKNguyen Jul 19 at 13:30
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    \$\begingroup\$ I think schematic capture implies that information (such as a netlist) can be extracted from the schematic. Drawing the schematic in Paint or a generic drawing program doesn't count as schematic capture. \$\endgroup\$ – Peter Bennett Jul 20 at 4:39
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    \$\begingroup\$ Imagine generally calling a pro photographer's job description as "just taking a picture". If that was the answer, it's not a great one unless one already knows the meaning. \$\endgroup\$ – Tony Stewart EE75 Jul 20 at 15:30
  • \$\begingroup\$ Sorry, no. This is not the answer, or it is a terribly partial/ambiguous one. I agree with @PeterBennett. A schematic capture program is not simply any fancy drawing program that is specialized for electrical circuits. It extracts the circuit information from the graphic input. It's a step in a process used for electrical CAD or simulation software. \$\endgroup\$ – Lorenzo Donati -- Codidact.com Jul 22 at 9:09
  • \$\begingroup\$ @TonyStewartEE75 "What is the meaning of light sensor pixel array readout?" "It just means taking a picture." \$\endgroup\$ – user253751 Jul 22 at 9:33
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tl; dr: 'schematic capture' is the process of taking a design created on another medium (e.g., paper) and re-creating a digital graphical version of it.

The term schematic capture is a holdover rooted in the evolution of schematic design practice and engineering culture.

How is schematic capture different from schematic design? Read on.

Schematic Design in the Pre-CAD Era

Before computer-aided design (CAD) became widespread, electronic designs were documented on hand-drawn schematics, most often drawn on a material called vellum, a tough, translucent paper that could stand up to erasing and be reproduced on a blueprint (diazo) machine.

Who drew schematics? Sometimes the design engineers (usually junior) would draw the schematics themselves, other times these would be drawn by draftspeople under the guidance of (usually more-senior) engineers, who would provide conceptual diagrams and sketches to the drafters to render as drawings.

Design in the CAD-Is-Expensive Era

With the introduction of CAD, these paper schematics were captured, or digitized, into electronic form, by operators trained to use the CAD platforms. (For several reasons, these operators tended to be draftspeople also. More about that in a bit.) The operators would re-draw the hand-drawn schematics in CAD to create the digital form.

The resulting computer-based schematics could then be used not only to replace vellum and blueprints (a monumental benefit in itself), but could also yield information for layout, simulation, assembly, and costing, much as it is the case today for modern schematic tools.

If this paper-into-CAD process sounds unwieldy, it was. It required careful attention to detail and multiple checks to ensure no errors crept in during to the the capturing process.

Why would anyone put up with such a process? Two reasons: cost, and culture.

Let's cover cost first. Early CAD software ran on large machines: initially time-share mainframes, then later minicomputers. Because schematic entry is graphical by its nature, to even use the software also required very expensive graphics terminals as well as faster connectivity to them.

Viewed another way, CAD terminals supplanted the drafting tables. It was thus a natural transition for draftspeople to move into driving software instead of pencil-on-vellum, carrying with them not just the institutional knowledge of drafting practice and standards, but also the layered management structure as a ‘service’ to engineering.

Which leads me to... culture.

Many electronic designers of the pre-CAD era (roughly until the late 1970s) were, ironically, computer-averse. They viewed CAD as an extension of drafting, seeing it a kind of 'secretarial work' (and, yes, there was sexism too.) Why, hadn't they already 'paid their dues' at the drafting table, only to have to learn to use a new tool to do something they 'have people' for?

This article offers an insight into how old-school engineers and executives felt about graphical terminals in the 1970s: https://crm.org/articles/xerox-parc-and-the-origins-of-gui

The Gift of Xerox PARC: The CAD-is-Affordable Era

This changed as schematic CAD platforms became both affordable and widely available (and, as some of the old dinosaurs retired or adapted.) Designers moved into entering and editing their own schematics themselves, quickly realizing the productivity gains of interacting with directly their design and its work products.

This sort of flow would be more correctly termed design entry, or just, design, as it is being driven directly by the engineer from the very beginning, interactively, with no 'digitizing' or 'capturing' step in between (and, no more 'CAD caves' staffed by draftspeople in the middle.)

Nevertheless the term 'schematic capture' still persists, even if only as a Cadence product name (they still use that term to mean design entry.)

But make no mistake: capture is not what actually happens for schematic design anymore. Instead it’s entry and editing, by the designer.

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Often the meaning of terms changes with technology but the rules can be traced to original practices.

Schematics were diagrammatic representations then in the general sense of a "hypothetical outline" excluding natural characteristics. First it was captured on paper then on microfiche or microfilm for condensed storage. The valid intersections demanded dots to prevent the photo-enlargment blurring that could mimic dots. Then "+" line intersections were avoided because of this optical expansion possible error.

Pretty much all the schematic capture standards originated from the US Military when they had the budget and manpower to define these standards with a massive library for every common electronic characteristic over 50 yrs ago. Refinements later came from IEEE from Industry.

Today it means something different, yet the rules persist in this logical, functional capture process to express a symbolic view of electrical concepts in the engineer's brain.

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In the old days Engineers used logical symbols common to the art of analog and digital workflow from left to right, with logical signal names with IC & pin numbers, plug (P#), Jack (J#)numbers and part values and power values with polarity and special features all scribbled down with notes for others to understand .

Then a draftsman would make it look pretty.

  • the engineer ensures it is error-free, readable with proper scaled fonts with logical function grouping, easy links to other system pages, include a wiring list and use std library symbols.

The aim was to make it logical , easy to read and logical for debug with test pins (TP#) . They also called it a logic diagram, because it wasn’t physical or complete to tell the whole story without notes or a design spec. It was also checked for errors and version controlled.

To make it useful it had to be easy to understand by others who might eventually have to assume what you meant for them to debug.

Now you are expected to learn all these skills by looking at all the best examples, company stds and do this yourself and make it compatible for a simulator with real parasitic L and C estimates.

Schematic Capture demands creativity and artistic flare learned from others.

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    \$\begingroup\$ Why do you have a bullet right after "make it look pretty and"? Typo? Joke? Other? \$\endgroup\$ – Yakk Jul 20 at 14:55

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