Lesson 2
Troubleshooting and Debugging VIs
Probe Tools
Na tio No na t fo l In r D str ist um rib en uti ts on
Use the Probe tool to check intermediate values on a wire as a VI runs.
Use the Probe tool if you have a complicated block diagram with a series of operations, any one of which might return incorrect data. Use the Probe tool with execution highlighting, single-stepping, and breakpoints to determine if and where data is incorrect. If data is available, the probe immediately updates and displays the data in the Probe Watch Window during execution highlighting, single-stepping, or when you pause at a breakpoint. When execution pauses at a node because of single-stepping or a breakpoint, you also can probe the wire that just executed to see the value that flowed through that wire. If you want a probe to display the data that flowed through the wire during the last VI execution, click the Retain Wire Values button on the block diagram toolbar.
Tip
Types of Probes
You can check intermediate values on a wire when a VI runs by using a generic probe, by using an indicator on the Controls palette to view the data, by using a supplied probe, by using a customized supplied probe, or by creating a new probe. (MathScript RT Module) You can view the data in a script in a MathScript Node as a VI runs by using a LabVIEW MathScript probe.
Note
Generic
Use the generic probe to view the data that passes through a wire. Right-click a wire and select Custom ProbeÂťGeneric Probe from the shortcut menu to use the generic probe.
The generic probe displays the data. You cannot configure the generic probe to respond to the data.
LabVIEW displays the generic probe when you right-click a wire and select Probe, unless you already specified a custom or supplied probe for the data type. You can debug a custom probe similar to a VI. However, a probe cannot probe its own block diagram, nor the block diagram of any of its subVIs. When debugging probes, use the generic probe.
Using Indicators to View Data
You also can use an indicator to view the data that passes through a wire. For example, if you view numeric data, you can use a chart within the probe to view the data. Right-click a wire, select Custom ProbeÂťControls from the shortcut menu, and select the indicator you want to use. You also can click the Select a Control icon on the Controls palette and select any custom control or
2-6 | ni.com