Cannot record signals continuously using "N Samples" mode

[meeu]

Hello,

I have two analog signals and a trigger setup on a PCI-6250 board to acquire 400 samples on every trigger at a rate of KHz.  When I try to record the signals, SignalExpress pops-up the following error:

"You cannot log data continuously from a device configured in "N Samples" mode if "Use relative initial time" is checked. You must uncheck "Use relative initial time"  (Advanced tab) or configure the device to acquire in continuous mode.

If you are recording the output of the Create Analog Signal step, make sure the "Repeated signal" checkbox is unchecked."

The only "advanced tab" I see is the "advanced timing" tab under the "Step Setup" tab.  In that tab is the "use relative timing" checkbox which is not checked.

I tried this with both SignalExpress 2009 and 2010 with no success.

Any ideas are appreciated.

[GarPar]

Hi meeu-

     The "use relative initial time" parameter is exclusive to an NI-SCOPE acquire step.  There is an advanced tab and a checkbox for this parameter.  Here is a blurb from the SignalExpress Help:

Use relative initial time—If checked, the initial time in the output waveform is set so that the trigger position (reference position) is at zero time. If unchecked, the initial time is the absolute time the waveform was acquired, as accurately as the hardware can determine it.

     Are you performing a NI-SCOPE acquisition at any step in your project?  You should just be performing an NI-DAQmx Acquire step as your first step.

     I hope this helps.  Best of luck with your application!

[meeu]

Hi Gary,

Thanks for the reply.  The only step in the project is the "DAQmx Acquire" using two analog voltage inputs.  Error occurs immediately after hitting the record button.

-meeu

[GarPar]

meeu-

     Interesting.  What version of SignalExpress are you using?  Can you post your code here so that we can try to replicate your error?

[meeu]

Gary,

Sorry for the delay.  I think I figured out why the error messaging is appearing.  It seems to be a bandwidth/buffer error.  If I have the number of samples set to 500 I get the mentioned error.  If I set the number of samples to 1.7k or higher, it seems to work fine.  This raises a question: is this something that is a limitation on the hardware as far as being able to record a certian number of samples per trigger and have enough time to read out a single buffer?  Or is this a software limitation/bug?

-meeu

[meeu]

I am using SignalExpress 2010 and have a 200KHz sample frequency.

-meeu

[meeu]

I was able to fix my problem for my application.  I originally had the trigger set for the Analog trigger.  There was no need for me to use the analog trigger so I instead used the digital trigger.  It now works for a sample size of 200 points and a sample rate of 200KHz.

So apparently it is a digital trigger versus analog trigger issue with a cryptic error message.  I would still be curious to know the reason for the limitation on analog trigger.

Kind Regards,

-meeu