LabVIEW for Everyone: Graphical Programming Made Easy and Fun (3rd Edition)

When you have both analog and digital signals that you wish to display together in a way that shows the timing relationships between the two, use a mixed signal graph, which may be found on the Modern>>Graph palette of the Controls palette (see Figure 8.92).

This graph accepts a cluster of any elements that you could wire into the waveform graph, XY graph, or digital graph, as shown in Figure 8.93.

It will plot all of these elements on one or more plot areas. You can add plot areas from the pop-up menu of an existing plot area by selecting Add Plot Area. Similarly, you can remove a plot area by selecting Remove Plot Area from the pop-up menu. The plot legend of a mixed signal graph is a tree control, having each plot's label and attribute display as child-nodes of the group name. You can drag and drop plots from one group to another; however, you cannot have analog and digital data in the same plot group. In fact, when you are wiring data on the block diagram to the mixed signal graph, LabVIEW will force you to have at least two plot areas if both analog and digital data are included (see Figure 8.94).

For an example of the mixed signal graph in action, see examples\general\graphs\Mixed Signal Graph.vi.

Multi-Plot Cursor

As we mentioned in the "Graph Cursors" section, the mixed signal graph has a special graph cursor mode called Multi-Plot mode (this cursor mode is available only to the mixed signal graph, and will be grayed out for other graph types). This type of graph cursor can report the Y values of multiple plots at a common X value. To create a multi-plot cursor, right-click on the cursor legend and select Create Cursor>>Multi-Plot, as shown in Figure 8.95. In order to report the Y values of a plot, the cursor must be configured to watch the plot, by selecting the plot name from the cursor label's pop-up menu under the Watch submenu. To watch all plots, select Watch>>All Plots from the cursor label's pop-up menu (see Figure 8.96).

Once you have created a multi-plot cursor, you can change its X value by grabbing the vertical cursor line and moving it horizontally (or by using the cursor mover). Watch how the cursor reports the Y values of each plot that it is watching, as shown in Figure 8.97.