How to synchronize AO and AI waveforms

[Ernest_Boitsov]

Hello all,

How i can accurately skip or determine a delay time that was marked on FrontPanel.PNG as red ellipse?
Or how i can "connect" sine sygnals by its start points using triggering?

I am using Labview 8.6 with a USB-4431 device and AI0 connect to AO0.

Thank You,
Ernest

[enderWiggin10]

Good afternoon Enest,

I have created a community example for you to reference that will bring in the analog output signal on an analog input channel.  I this example, they are both synchronized and the signal start points will line up.

Best,

[enderWiggin10]

Hello Ernest,

I apologize for my first post, I did not realize you were using a DSA card.  With our DSA cards there will be a given delay for each card depending on the ADC filtering.  You can reference the USB-4431 manual for this information; it is listed at 38 samples (nominal) of delay.  With that said, you can choose to throw away the first 38 samples of the data array to accomplish this by splitting the array after the 38th element, and only graphing the samples thereafter.  It might need to be fine tuned a bit, so 38 samples is a nominal value.

Best,

Message Edited by cyclone2k9 on 04-22-2010 03:42 PM

[Ernest_Boitsov]

Thank you for your help, Adam F!

After reading these documents:

Why Is My Data Delayed When Using DSA Devices? (http://digital.ni.com/public.nsf/allkb/F989B25FF6CA55C386256CD20056E27D)

What is the Difference Between Analog and Digital Triggered Acquisition for the NI 447x Boards? (http://digital.ni.com/public.nsf/allkb/EA42429C0BF5510C86256DA9007876E3)

I had a few questions.

I always get approximately 100 (not 38) pretrigger samples that I did not ask for. Why?

How can I change in current problem Digital Triggered Acquisition (source of the trigger - ai/StartTrigger ) to Analog Triggered Acquisition?

Can I turn off or disable Low-Frequency Alias Rejection?

Best regards,
Ernest

[enderWiggin10]

Hi Ernest,

I have tried to disable the filtering on the USB device using a channel property node in LabVIEW, but it is not possible.  It is available on the 447x DSA devices which are PCI or PXI form factor.

You can change a digital trigger to an analog trigger by clicking on the trigger box below the VI Icon specifying Start»Analog Edge.  However, you can use this on an analog input task, and not on a digital input task. 

You might be getting more delay due to the sample rate of your acquisition, which can affect this amount of unusable data points.

Best,