Creating Tasks with Common Start Time with cDAQ-9189

Updated Aug 17, 2018

Reported In

Hardware

  • cDAQ-9189
  • cDAQ-9185

Issue Details

I have two cDAQ-9189 daisy chained with two analog input modules in each chassis. I am creating one task per module configured to start the acquisition at the same time by using DAQmx Start Trigger VI instanced as Start Time, and sharing the same timestamp to all the tasks. I noticed that the Start Trigger terminal is different for each task. Should all of the tasks have the same Start Trigger terminal? Are the tasks synchronized?

Solution

Having a different Start Trigger terminal for each task is normal as each task uses a different timing engine. The NI cDAQ-9189 chassis provide three timing engines for analog input (te0, te1, and ai). The Sample Clock and Sample Clock Timebase, as well as the Start, Reference, and Pause triggers, exist on each timing engine. Therefore, the names of the output terminals for those signals include the associated timing engine.

In each chassis the timing engines share the same clock source and between chassis this source clock is phase-aligned trough TSN Network. Thus by adding a start trigger to the task, the data is synchronized. For more information about synchronization with TSN devices refer to How to Achieve High-Accuracy Measurements With NI-DAQmx-Based TSN Devices.

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