Control Loops Diagram

Terminology

A block diagram is a pictorial representation of the cause and effect relationship between the input and output of a physical system. A block diagram provides a means to easily identify the functional relationships among the various components of a control system.

The simplest form of a block diagram is the block and arrows diagram. It consists of a single block with one input and one output (Figure 5A). The block normally contains the name of the element (Figure 5B) or the symbol of a mathematical operation (Figure 5C) to be performed on the input to obtain the desired output. Arrows identify the direction of information or signal flow.

block-and-arrows-fig-5.png

Although blocks are used to identify many types of mathematical operations, operations of addition and subtraction are represented by a circle, called a summing point. As shown in Figure 6, a summing point may have one or several inputs. Each input has its own appropriate plus or minus sign. A summing point has only one output and is equal to the algebraic sum of the inputs.

summing-points-fig-6.png

A takeoff point is used to allow a signal to be used by more than one block or summing point (Figure 7).

takeoff-point-fig-7.png

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