Scope, Floating Scope (Simulink Reference)

Display signals generated during a simulation

Library

Sinks

Description

The Scope block displays its input with respect to simulation time. The Scope block can have multiple axes (one per port); all axes have a common time range with independent y-axes. The Scope allows you to adjust the amount of time and the range of input values displayed. You can move and resize the Scope window and you can modify the Scope's parameter values during the simulation.

When you start a simulation, Simulink does not open Scope windows, although it does write data to connected Scopes. As a result, if you open a Scope after a simulation, the Scope's input signal or signals will be displayed.

If the signal is continuous, the Scope produces a point-to-point plot. If the signal is discrete, the Scope produces a stair-step plot.

The Scope provides toolbar buttons that enable you to zoom in on displayed data, display all the data input to the Scope, preserve axis settings from one simulation to the next, limit data displayed, and save data to the workspace. The toolbar buttons are labeled in this figure, which shows the Scope window as it appears when you open a Scope block.

Note Do not use Scope blocks inside library blocks that you create. Instead, provide the library blocks with output ports to which scopes can be connected to display internal data.

Displaying Vector Signals

When displaying a vector or matrix signal, the Scope assigns colors to each signal element in this order: yellow, magenta, cyan, red, green, and dark blue. When more than six signals are displayed, the Scope cycles through the colors in the order listed.

Y-Axis Limits

You set y-limits by right-clicking an axis and choosing Axes Properties. The following dialog box appears.

Y-min: Enter the minimum value for the y-axis.
Y-max: Enter the maximum value for the y-axis.
Title: Enter the title of the plot. You can include a signal label in the title by typing %<SignalLabel> as part of the title string (%<SignalLabel> is replaced by the signal label).

Time Offset

This figure shows the Scope block displaying the output of the vdp model. The simulation was run for 40 seconds. Note that this scope shows the final 20 seconds of the simulation. The Time offset field displays the time corresponding to 0 on the horizontal axis. Thus, you have to add the offset to the fixed time range values on the x-axis to get the actual time.

Autoscaling the Scope Axes

This figure shows the same output after you click the Autoscale toolbar button, which automatically scales both axes to display all stored simulation data. In this case, the y-axis was not scaled because it was already set to the appropriate limits.

If you click the Autoscale button while the simulation is running, the axes are autoscaled based on the data displayed on the current screen, and the autoscale limits are saved as the defaults. This enables you to use the same limits for another simulation.

Note Simulink does not buffer the data that it displays on a floating Scope. It can therefore scale the contents of a floating Scope only when data is being displayed, i.e., when a simulation is running. When a simulation is not running, Simulink disables (grays) the Zoom button on the toolbar of a floating Scope to indicate that it cannot scale its contents.

Zooming

You can zoom in on data in both the x and y directions at the same time, or in either direction separately. The zoom feature is not active while the simulation is running.

To zoom in on data in both directions at the same time, make sure the leftmost Zoom toolbar button is selected. Then, define the zoom region using a bounding box. When you release the mouse button, the Scope displays the data in that area. You can also click a point in the area you want to zoom in on.

If the scope has multiple y-axes, and you zoom in on one set of x-y axes, the x-limits on all sets of x-y axes are changed so that they match, because all x-y axes must share the same time base (x-axis).

This figure shows a region of the displayed data enclosed within a bounding box.

This figure shows the zoomed region, which appears after you release the mouse button.

To zoom in on data in just the x direction, click the middle Zoom toolbar button. Define the zoom region by positioning the pointer at one end of the region, pressing and holding down the mouse button, then moving the pointer to the other end of the region. This figure shows the Scope after you define the zoom region, but before you release the mouse button.

When you release the mouse button, the Scope displays the magnified region. You can also click a point in the area you want to zoom in on.

Zooming in the y direction works the same way except that you click the rightmost Zoom toolbar button before defining the zoom region. Again, you can also click a point in the area you want to zoom in on.

Note Simulink does not buffer the data that it displays on a floating scope. It therefore cannot zoom the contents of a floating scope. To indicate this, Simulink disables (grays) the Zoom button on the toolbar of a floating scope.

Saving the Axes Settings

The Save axes settings toolbar button enables you to store the current x- and y-axis settings so you can apply them to the next simulation.

You might want to do this after zooming in on a region of the displayed data so you can see the same region in another simulation. The time range is inferred from the current x-axis limits.

Scope Parameters

You can change axis limits, set the number of axes, time range, tick labels, sampling parameters, and saving options by choosing the Parameters toolbar button.

When you click the Parameters button, this dialog box appears.

The dialog box has two panes: General and Data history.

General Parameters

You can set the axis parameters, time range, and tick labels in the General tab. You can also choose the floating scope option with this tab.

Number of axes: Set the number of y-axes in this data field. With the exception of the floating scope, there is no limit to the number of axes the Scope block can contain. All axes share the same time base (x-axis), but have independent y-axes. Note that the number of axes is equal to the number of input ports.
Time range: Change the x-axis limits by entering a number or auto in the Time range field. Entering a number of seconds causes each screen to display the amount of data that corresponds to that number of seconds. Enter auto to set the x-axis to the duration of the simulation. Do not enter variable names in these fields.
Tick labels: You can choose to have tick labels on all axes, on one axis, or on the bottom axis only, using the Tick labels list.
Floating scope: Selecting this option turns a Scope block into a floating scope. A floating scope is a Scope block that can display the signals carried on one or more lines. You can create a Floating Scope block in a model either by copying a Scope block from the Simulink Sinks library into a model and selecting this option or, more simply, by copying the Floating Scope block from the Sinks library into the model window. The Floating Scope block has the Floating scope parameter selected by default.; To use a floating scope during a simulation, first open the scope. To display the signals carried on a line, select the line. Hold down the Shift key while clicking another line to select multiple lines. It might be necessary to click the Autoscale data button on the floating scope's toolbar to find the signal and adjust the axes to the signal values. Or you can use the floating scope's Signal Selector (see Signal Selector) to select signals for display. The Signal Selector allows you to select signals anywhere in your model, including unopened subsystems.; You can have more than one floating scope in a model, but only one set of axes in one scope can be active at a given time. Active floating scopes show the active axes by making them blue. Selecting or deselecting lines affects the active floating scope only. Other floating scopes continue to display the signals that you selected when they were active. In other words, nonactive floating scopes are locked, in that their signal displays cannot change.; To specify display of a signal on one of the axes of a multiaxis floating scope, click the axis. Simulink draws a blue border around the axis.; Then click the signal you want to display in the block diagram or the Signal Selector. When you run the model, the selected signal appears in the selected axis.; If you plan to use a floating scope during a simulation, you should disable signal storage reuse. See "Signal storage reuse" in Optimizations for more information.
Sampling: To specify a decimation factor, enter a number in the data field to the right of the Decimation choice. To display data at a sampling interval, select the Sample time choice and enter a number in the data field.

Controlling Data Collection and Display

You can control the amount of data that the Scope stores and displays by setting fields on the Data History pane.

You can also choose to save data to the workspace in this tab. You apply the current parameters and options by clicking the Apply or OK button. The values that appear in these fields are the values that are used in the next simulation.

Limit data points to last: You can limit the number of data points saved to the workspace by selecting the Limit data points to last check box and entering a value in its data field. The Scope relies on its data history for zooming and autoscaling operations. If the number of data points is limited to 1,000 and the simulation generates 2,000 data points, only the last 1,000 are available for regenerating the display.
Save data to workspace: You can automatically save the data collected by the Scope at the end of the simulation by selecting the Save data to workspace check box. If you select this option, the Variable name and Format fields become active.
Variable name: Enter a variable name in the Variable name field. The specified name must be unique among all data logging variables being used in the model. Other data logging variables are defined on other Scope blocks, To Workspace blocks, and simulation return variables such as time, states, and outputs. Being able to save Scope data to the workspace means that it is not necessary to send the same data stream to both a Scope block and a To Workspace block.
Format: Data can be saved in one of three formats: Array, Structure, or Structure with time. Use Array only for a Scope with one set of axes. For Scopes with more than one set of axes, use Structure if you do not want to store time data and use Structure with time if you want to store time data.

Printing the Contents of a Scope Window

To print the contents of a Scope window, open the Scope Properties dialog by clicking the Print icon, the rightmost icon on the Scope toolbar.

Signal Selector

The Signal Selector allows you to select the signals to be displayed in the floating scope. You can use it to select any signal in you model, including signals in unopened subsystems. To display the Signal Selector, first start simulation of your model with the floating scope open. Then right-click your mouse in the floating scope and select Signal Selection from the pop-up menu that appears. The Signal Selector appears.

The Signal Selector contains two panes. The left pane allows you to display signals of any subsystem in your model. The signals appear in the right pane. The right pane allows you to select the signals to display in the floating scope.

To select a subsystem for viewing, click its entry in the Model hierarchy tree or use the up or down arrow keys to move the selection highlight to the entry. To show or hide the subsystems contained by the currently selected subsystem, click the +/- button next to the subsystem's name or press the forward or backward arrow keys on your keyboard. To view subsystems included as library links in your model, click the Library Links button at the top of the Model hierarchy pane. To view the subsystems contained by masked subsystems, click the Look Under Masks button at the top of the pane.

The Signals pane shows all the signals in the currently selected subsystem by default. To show named signals only, select Named signals only from the List contents control at the top of the pane. To show test point signals only, select Test point signals only from the List contents control. To show only signals whose signals match a specified string of characters, enter the characters in the Show signals matching control at the bottom of the Signals pane and press the Enter key. To show the selected types of signals for all subsystems below the currently selected subsystem in the model hierarchy, select the Current and Below button at the top of the Signals pane.

The Signals pane by default shows the name of each signal and the number of the port that emits the signal. To display more information on each signal, select the Detailed view button at the top of the pane. The detailed view shows the path and data type of each signal and whether the signal is a test point.

To select or deselect a signal in the Signals pane, click its entry or use the arrow keys to move the selection highlight to the signal entry and press the Enter key. You can also move the selection highlight to a signal entry by typing the first few characters of its name (enough to uniquely identify it).

Note You can continue to select and deselect signals on the block diagram with the Signal Selector open. For example, shift-clicking a line in the block diagram adds the corresponding signal to the set of signals that you previously selected with the Signal Selector. Simulink updates the Signal Selector to reflect signal selection changes you have made on the block diagram. However, the changes do not appear until you select the Signal Selector window itself.

Data Type Support

A Scope block accepts real signals of any data type, including fixed-point data types, except int64 and uint64. The Scope block accepts homogeneous vectors.

Characteristics

Sample Time
Inherited from driving block or can be set

States
0

Sample Time	Inherited from driving block or can be set
States	0

Saturation Selector