Synchronizing Mixed Signal Oscilloscope Acquisition with Function Generator Output at NI VirtualBench

Updated Mar 13, 2018

Reported In

Software

  • VirtualBench (Legacy)
  • VirtualBench (Legacy) 2.0
  • VirtualBench (Legacy) 2.5

Issue Details

Can Mixed Signal Oscilloscope (MSO) acquisition be synchronized with the Function Generator (FGEN) output of the VirtualBench, or can they at least be started at the same time?

Solution

In order to achieve the best synchronization between the MSO and FGEN, you will need to ensure that both sessions start at the same time.
You can implement this by configuring a digital edge trigger for the MSO session, which can then use the start event of the FGEN session as a start trigger. Additionally, the sample clocks generated for MSO and FGEN sessions both reference the same onboard oscillator, and therefore should be phase coherent (they are not, however, guaranteed to be phase aligned and will more than likely be offset by some small amount).

As of NI-VirtualBench Application and Driver 1.1.1, you can export and route the FGEN Start Event internally by simply selecting the FGEN Start Event as the Trigger Source for the MSO’s Digital Edge Trigger as shown in Figure 1.
 
Figure 1. 
 
In order to have this option in the drop down section, you must have change the settings. 
To enable Advanced Channels, first right-click the Trigger Source control and select I/O Name Filtering, then ensure that the Advanced Channels check box is checked. Figure 2 and 3 below show the step.

Figure 2.

Figure 3.
 

Additional Information

​Keep in mind that the FGEN itself cannot accept a trigger to start. This means that the FGEN start will be dependent on software timing and there will be some inherent amount of latency when the FGEN’s signal actually gets generated. Also, you will want to make sure that the MSO is ready to accept the trigger before the FGEN sends it.

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