Caveats and Recommendations When Using Custom Probes

The following list describes some of the caveats and recommendations to consider when you create and use custom probes:

• Custom probes only execute when data flows through the wire. That is, although you can operate the controls on a custom probe at any time, programmatic responses to the changed control values occur only when the probe receives data from the wire.
• 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.
• Save probes in the labview\user.lib\_probes\default or the Default Data\Probes directories. Probes saved in the labview\user.lib\_probes\default directory are available to anyone running LabVIEW on the computer remotely. This directory is useful for public probes. Because the Default Data directory changes based on which user is logged in to the computer, National Instruments recommends you save non-public probes in this directory.
• The main block diagram pauses until the probe finishes execution. Avoid using loops or Event structures in custom probes as these elements can increase the time it takes the probe to finish executing.
• Be careful when using uninitialized shift registers in custom probes. Even if a VI is non-reentrant, when that VI is used as a probe, all uninitialized shift registers behave the same as reentrant VIs. Each probe retains the last value of the loop and does not share these values with other instances of the same probe.