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Phase Delay Between Multiple NI-TClk Synchronized Digitizers When Using a Trigger Delay

Hardware: Modular Instruments>>High-Speed Digitizers (Scopes)

I am trying to synchronize two NI Digitizers using one of the NI-SCOPE Synchronization Examples from the NI Example Finder. If I add a Trigger Delay I notice that I have a phase offset between devices. Why does this happen?

The NI-SCOPE NI-TClk based synchronization examples only configure a trigger for the master device. This is typically acceptable, since NI-TClk is used to synchronize the slave devices to the master. However, when using a large trigger delay, like a 1 second delay, it becomes difficult for NI-TClk to synchronize the two devices correctly. To fix this issue please follow the steps below:
  1. Locate the case structure which checks for the loop iteration. The loop iteration indicates which device the code is dealing with.
  2. Make sure the "0" case is being displayed as shown in the image below.
  3. Right-click on the border of the case structure and select "Remove Case Structure." This will allow a trigger to be configured for each device.

Note: The above changes should be implemented only if using the following examples:
  • niScope EX Multi-Device Configured Acquisition (TClk).vi
  • niScope Ex Multi-Device Different Sample Clock Rates (TClk).vi
  • niScope EX Multi-Device External Clocking (TClk).vi
  • niScope EX Multi-Device Generic Sync (TClk).vi
After making this change you should no longer see a phase delay between the devices when using a trigger delay.

Related Links:
NI High-Speed Digitizers Help: Trigger Delay
NI High-Speed Digitizers Help: niScope Configure Trigger (poly)
Example Program: niScope EX Multi-Device Multi-Chassis TClk Example in LabVIEW
Specifications Explained: NI Oscilloscopes and Digitizers


Report Date: 01/28/2014
Last Updated: 10/04/2017
Document ID: 6HRHK8AO

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