Acquisition "delay" in synchronising PXI5105 and PXI5412

[TCUENGR]

Hi Friends,

I've attached the VI I'm working with for reference.  In it I'm attempting to initiate acquisition as soon as the ARB generates the hanning window burst signal.  

The intention is to capture time-of-flight information.

This mostly works except there seems to be a short delay between when the signal is generated and when acquisition actually begins.  I attempted to use the reference position to capture pre-trigger samples to no avail.  Varying the value from 0 to 100 seems to have no effect. 

I've attached a jpeg to illustrate what I'm seeing.

Any help would be very much appreciated.

[nayer]

Hi There,

I did try running your VI. Since after update the data doesnot line up as there is not 'Tclk sync' done. I did modified it a bit after that the data generated and read were lined up, at the same time. keep us posted

Cheers

NI-khil

Message Edited by NIyer on 03-22-2010 04:37 PM

[TCUENGR]

Hi NIyer,

Thanks for your help.  However I tried using your modified version again to no avail.  The synchronization still doesn't quite line up.

I've attached a jpeg to illustrate.  Does it work on your computer?

[nayer]

Hello.

You are right  I am able to reproduce the issue on my side with the same hardware setup. Interesting I found is if you reduce the sample rate of the AWG to less than the half of the sample rate of scope, the data do align, i.e SR of AWG is  20M and SR of digitizer is 60M the data do line up, but faster than that it does miss few data point. I will look little more into this and will update you. 

Regards

NI-khil

[TCUENGR]

Kudos NIyer,

Thanks for trying.  Please update me of your findings.

I'm very thankful for your help.

[nayer]

Hello There,

I have found a solution for you, the issue was how  the scope transitions through the states, and how it fetches the data. In order to fetch those missing points add Fetch Relative To property node and set it to 'Start'. I have attached the modified VI that work perfectly fine. 

Cheers

NI-khil 

Kudos always help 😉

[nayer]

Hello

Here is correct code.

NI-khil

[TCUENGR]

Hi NIyer,

Sorry for the delay.  Your solution works.

I also found a solution myself.  I completely took out tclk, pulled the session references from the ARB and DAQ and set the ARB to export a trigger.  That trigger is then pulled by the DAQ which starts acquiring the same time the excitation is generated.

I hope that makes sense.  I'm routing the triggers through the PXI chassis. 

See the attachment.

While both VI's work, I will select yours as the solution as I appreciate your effort.  

Cheers.

[mfdupuis]

Hey guys,

I know I'm digging up old material here, but I was wondering if you could give me a hand. I'm trying to run a program that does almost the exact same thing your program does, but I'm having trouble with the trigger as well. My scope reads the correct signal, but it's bouncing all over the place because of the lack of trigger. I found that using an analog trigger and setting that to a certain voltage held the signal in place, but this also eliminates the first part of my signal that is below that trigger.

I looked at your code TCUENGR, and tried applying the trigger pieces to mine without success. I attached my code to this message. The Fgen is in the top outside of any loop, and the Scope is in the bottom left-hand corner of that big while loop. You can ignore those four case structures, they're only there to save the different scope channels with under different file names.

Thanks,

Marc

[TCUENGR]

Dear mfdupuis,

Since the writing of this thread I've moved to a position that no longer involves me with NI software.  As such I will not be able to offer support on this topic, but I wish you best of luck in finding a solution.  

Perhaps consider contacting NI support, as they were helpful in assisting us when we ran into problems.