There are a
number of considerations when performing triggering and timing operations using
PXI modules. If you want to confirm the proper procedure for implementing these
functions you can view a document that discusses using PXI timing and
triggering functionality here. Additionally, for tighter synchronization, I
would recommend that you share the sample clock, as well as the trigger pulse, between
the devices. This process is described in the document previously referenced,
but it would allow you to ensure that your samples were occurring on the same
time-base as well as at the same rate. You may need to add an niScope Configure
Clock.vi to your block diagram, but it should provide better synchronization
wanted to follow up on some of the information you had posted in the attached
documents. In the first slide of your PowerPoint presentation, where the two signals
appear to be different, what is the frequency of your input signal? That is to
say, which of the data appears to be correct? The PXI-6120 on top or the
I hope this information is helpful. Let me know if there is anything else I can do.
Regarding your qns, the input wave is 1khz and the graph for the PXi-6120 is correct, the graph above is correct. I will try to see what I can improve on your suggestions. Thanks for the help.
I have removed the export trigger vi from the code and the Scope is not triggered; hence i think that the triggering is working. And also, i discovered that the minimum sample rate for NI-5922 is 50KS/s. This may be the reason why there is a difference in the graphs plotted when i used a sample rate of 10Ks/s.
However I am still having trouble getting both the cards to be sychronised. The main reason is that one card is using NI DAQ-mx and the other is using NI-Scope. I have trouble telling them to share the sample clock. The samples and documents which i found only described cases where both cards are using DAQ-mx. Can you advise me on the matter?
Default Value: 50%"In your diagram, you have left this input unwired. Therefore, the VI will use the default value of 50% and will use the trigger from the PXI-6120 as the reference event. I believe this is causing the waveforms you demonstrated in your post. I have attached a screen shot of some code that should change this behavior. By changing the reference position to 0, the trigger should occur at the beginning of the waveform. You'll notice I have also set a value for the trigger slope input on niScope Configure Digital Trigger.vi. I have placed a constant "Positive" at this input because I wanted to be sure the trigger was occurring on the positive edge. I would recommend that you implement these changes and examine the behavior of your code then. Let me know how this works out for you.
the reference position seems to be the problem. Thanks for the advice. However what exactly does the reference position means? So can i assume that the 2 cards are synchronised?