Software Trigger Inconsistent Reference

[degree]

Hi,

I have three signals (ai0, ai1 and ai2) at 6000 samples at a data rate of 25k.  ai0 is a trigger signal and reaches an amplitude of 4V the other two (ai1 and ai2) occur about 10ms after ai0 and do not exceed 0.2V.

I am trying to record ai1 and ai2 using a software trigger and a pre-trigger of 2000 samples as a reference point.

I select the, "run" (-->) button and when the system is triggered, the desired graph is observed for a split second but the .txt file(s) output show only the signal shortly after the signal has passed, this happens about 50% of the time.

When the desired signal does fall within the window, it does not have a set reference point.  This all seems to be the one problem regarding the, "run" button not reading with respect to ai0 but erratically around it.

I am a university student working with LabView for the first time for my thesis,  please let me know if there is any more information I can provide.

Regards

Kumaresan.S

[Norbert_B]

Kumaresan,

please post your current vi(s) and tell us which hardware you are using.

I'd say that you either have a timing issue or a race condition of some sort...

Norbert 

[muks]

Can you be specific in letting us know the exact value of "split second"? Also cant it be automated using a while loop and the trigger exits the while loop and passes the control to the next stage instead of u pressing the run button?

[degree]

I'm using LabVIEW 2.0.0 for a really straightforward task and the issue apperars to be simply that I was not inputting the triggered data to the "Save ASCII/LVM" - I am now getting the expected plots consistently.

Problem solved (? Cautiously)

I will elaborate what I am doing for the record; the event I am recording ~10 instances of a single discrete event which occurs for ~40ms every 35 seconds.  Initialising the system.  Forgive my naivete but I was not aware that a loop was possible or necessary in my case - the use of LabVIEW is not the focus but simply a means to an end.

The Steps being used are "DAQmx Acquire" - "Software Trigger" - "Save ASCII/LVM".  The physical device to which the signals arrive at before the computer is a National Instruments BNC-2110 "Analog I/O" and "Digital & Timing I/O" panel.

The "split second" after appears to only have been the random variation in position of the raw input which explains why the signal would not keep a constant reference point.

I truly appreciate your immediate responses.

Thanks and regards,

Kumaresan.S

[RavensFan]

Are you really using LabVIEW 2.0?  If so, I think you are long overdue for an upgrade.

I don't think you are using LV2 because DAQmx wouldn't be able to work with it.

[muks]

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I don't think you are using LV2 because DAQmx wouldn't be able to work with it.

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I too think so

[degree]

No, I triple checked the version - it's 2.0, this computer is ancient and has been in the lab for what I believe would be about a decade.  The first step I use is "DAQmx Acquire: Analog Input".

[RavensFan]

Could you be using Signal Express 2.0???

Please upload your VI.  Also, attach a screenshot of your VI has a .png or .jpg.