Error using pretrigger when capturing more than one channel

[Jackson_Peacock]

I am having problems acquiring data with pretrigger samples when capturing more than one channel, using NI-PXI-6071E hardware and Labview's Analog Input VIs (Legacy NI-DAQ).

My goal is to trigger on one signal, while capturing another. Unfortunately, I cannot use the PFI0 for external triggering, as our cables/hardware have already been built, so I must use an analog input channel as the trigger. I understand that to do so I must capture both channels, and the channel that I wish to trigger off of must be the first channel in the list.

If I trigger and capture on the same channel (tried 1-4) then it works great, regardless of the number of pre-trigger samples set. If I capture more than one channel (passing the trigger channel first), with no pretrigger samples set, then triggering and capturing both work fine. However, if I do the same with the pretrigger sample > 0 I get the following error:

Error -10621 occurred at AI Control. Possible reason(s):
NI-DAQ LV: The specified trigger signal cannot be assigned to the trigger resource.

I don't se any such limitation explained in the user manual, and searching the forum, I have found a few other people that had the same problem but they did not have solutions. Any ideas?

[EricS. · Accepted solution]

Hi Jackson,

Unfortunately that is a hardware limitation when doing analog reference triggering through one of the AI lines.

Please reference this Knowledgebase. Specifically the second paragraph says

The -10621 error will immediately be displayed upon running the VI if you try to assign pre-trigger scans while scanning multiple channels and using one of the inputs as your trigger channel.

Details are explained in the third paragraph:

Because all the inputs are multiplexed before being sent to the analog trigger circuitry, it is possible that the proper trigger conditions on the trigger channel could be missed while the device is multiplexing another channel. If this happens, the trigger will not be detected. 

More of this is explained in the E-Series User Manual  on page 10-3.  Specifically the second paragraph of the section titled "Analog Input Channel."

Eric S.

[Jackson_Peacock]

Thank you! I had read that page in the manual but failed to associate "analog reference or pause trigger" with pretrigger sampling. The knowledgebase entry did a very good job of explaining the limitation and the reason behind it. I will talk to our engineers and see if they would rather redesign the cables to use PFI0 or live without pretriggering.