Roymech engineering encyclopedia

Electrical Control Diagrams

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Electrical Control Diagrams


The following notes relate to BS 7845:1996 ..Guide to the use of BS 3939 and BS EN 60617
There are a number of diagrams & drawings associated with Electrical /Control engineering some of which are involved to some level with mechanical engineering.

A list of the diagrams covered by these notes is provided below

  1. Block Diagram
  2. Circuit Diagram
  3. Connection Diagrams
  4. Interconnection Diagrams

Block Diagram

A block diagram is a simple diagram in which an installation or equipment system together with its functional relationships are represented by block symbols or outlines with annotation without necessarily showing connections.

Circuit Diagram

Circuit diagrams are completed to show the full functioning of a circuit showing all its essential components and connections by means of graphical symbols.  It shows the operations without necessarily showing the physical layout.

Connection Diagram

A connection diagram shows all of the connections between components. This diagram assists in the actual wiring of circuits.

Interconnection Diagram

An interconnection diagram represents the connections between the different units of and installation.   Its purpose is to show the external connections of a unit.  The internal connections are shown on a wiring diagram.

Links Providing information on Drawing Diagrams and Symbols
  1. Electrical Symbols and Line Diagrams ... pdf download - Excellent Presentation in some detail.
  2. Red-Bag-Electrical Design Standard Symbols ... Download containing a large comprehensive set of symbols
  3. Units and Symbols for Electrical and Electronic Engineers - IET ... A very good quality resource. Lots of info.