Inconsistent Triggering on PCI 6052E DAQ card

[ponnaboy]

Hi,
I am working on a VI that generates a 10 ms pulse on analog output channel (DAC0OUT) and simultaneously acquires data on the analog input channels based on a digital trigger.I see some inconsistency in the triggering....it(PCI 6052E) is missing some of the triggers.If I trigger at a slower rate(1/2 trigger/sec) or trigger at a faster(rate) or at a constant rate it seems to work fine.

[nestor-sg]

Shiv,
We couldn't really figure out what you really mean with "rate" because you include a half trigger per second and it doesn't tell us much about it, we will need a lot more of detail of what is your program doing and how... and is not enough to look into a VI that we didn't make, hope you understand our point. I would really recommend that you give us call instead of using a text based message it will be a lot easier to understand the overall behaviour of your system.

For the info on how to call us use: www.ni.com/ask

Thanks and we expect to hear from you,

Nestor Sanchez
Applications Engineer
National Instruments

[ponnaboy]

Nestor,
I am working on a Data acquisition program using PCI 6052E DAQ card.It is a triggered acquisition to acquire data on the analog input channels(ACH0 and ACH2) using the BNC-2090 adapter.The trigger is a TTL pulse on PFI0 pin.The trigger is obtained by passing a mechanical signal from a strain gauge through a transducer.
strain gauge->transducer->coulbourn discriminator->TTL
pulse.
I need to acquire data on the analog input channel based on the rising edge of this digital trigger and write it to a file.Simultaneously I would also like to send out a 10 ms (5 V)pulse on the DAC0OUT based again on the same trigger.
My problem is even though I am able to see the trigger being generated on the oscilloscope every time, I am not able to acquire dat
a on Analog i/p channel and send 10 ms pulse on DAC0OUT channel sometimes.If I trigger at 1 or 2 triggers per second it works fine and if I trigger too fast it works fine.
Thanks for your help!
-shiv

[nestor-sg]

Shiv,

Sorry for this delay, I haven't answer back because I now attend LabVIEW area only, so you may want to write to the DAQ supporters directly by going to www.ni.com/ask and choose to Email NI Engineers. Your system seems to be working fine at different speeds of the trigger that's curious so probably you may really want to email DAQ staff directly or even give us a call so we can troubleshoot this interactively.

Take a decision and we'll be here for support.

Good luck!...

Nestor Sanchez
Applications Engineer
National Instruments

[Erin_B.]

Hi,

A couple of things could be going wrong here. First, you are not controlling the execution flow of your program with regards to the analog input and output. Depending on how fast each component executes, AI Read could already be blocking by the time AO Start is called. At that point, your AO would not be started because AI Read will not allow any other DAQ functions to execute until it completes and all of the data requested has been acquired.

Second, you could be missing triggers because your acquisition is not be configured quickly enough. This is unavoidable due to the amount of time that it takes to restart your acquisition.

I would recommend stepping through the execution of your loop and tightening up the timing of the loop. Another sugges
tion is to break it up into pieces to further troubleshoot the problem. Write the AI component and make sure that the timing is correct. Then add in the AO component and make the AI Start call dependent on the completion of AO Start to ensure that it starts before AI Read is called. You may also save time on the AI reconfiguration by breaking up AI Start into its components and moving AI Clock Config and AI Trigger Config outside of the loop. The same can also be done for the AO configuration components.

Hope this helps.

Regards,
Erin