Signal Basics :: Working with Signals (Using Simulink)

Using Simulink

Signal Basics

This section provides an overview of Simulink signals and explains how to specify, display, and check the validity of signal connections.

About Signals

Simulink defines signals as the outputs of dynamic systems represented by blocks in a Simulink diagram and by the diagram itself. The lines in a block diagram represent mathematical relationships among the signals defined by the block diagram. For example, a line connecting the output of block A to the input of block B indicates that the signal output by B depends on the signal output by A.

Note It is tempting but misleading to think of Simulink signals as traveling along the lines that connect blocks the way electrical signals travel along a telephone wire. This analogy is misleading because it suggests that a block diagram represents physical connections between blocks, which is not the case. Simulink signals are mathematical, not physical, entities and the lines in a block diagram represent mathematical, not physical, relationships among signals.

Creating Signals

You can create signals by creating source blocks in your model. For example, you can create a signal that varies sinusoidally with time by dragging an instance of the Sine block from the Simulink Sources library into the model. See Sources in the online Block Libraries reference for information on blocks that you can use to create signals in a model. You can also use the Signal & Scope Manager to create signals in your model without using blocks. See The Signal & Scope Manager for more information.

Signal Labels

A signal label is text that appears next to the line that represents a signal that has a name. The signal label displays the signal's name. In addition, if the signal is a virtual signal (see Virtual Signals) and its Show propagated signals property is on (see Show propagated signals), the label displays the names of the signals that make up the virtual signal.

Simulink creates a label for a signal when you assign it a name in the Signal Properties dialog box (see Signal Properties Dialog Box"). You can change the signal's name by editing its label on the block diagram. To edit the label, left-click the label. Simulink replaces the label with an edit field. Edit the name in the edit field, the press Enter or click outside the label to confirm the change.

Displaying Signal Values

As with creating signals, you can use either blocks or the Signal & Scope Manager to display the values of signals during a simulation. For example, you can use either the Scope block or the Signal & Scope Manager to graph time-varying signals on an oscilloscope-like display during simulation. See Sinks in the online Block Libraries reference for information on blocks that you can use to display signals in a model.

Signal Data Types

Data type refers to the format used to represent signal values internally. The data type of Simulink signals is double by default. However, you can create signals of other data types. Simulink supports the same range of data types as MATLAB. See Working with Data Types for more information.

Working with Signals Signal Dimensions