Acq-Ext.c example with a PXI-4462

[jmevans]

Hello.

 I have a PXI chassis with a PXI-4462 installed and I'm writing in CVI (2009) using the DAQmx API. I'm trying to acquire a waveform which is synchonized with a trigger signal, so I'm starting with the Acq-Ext.prj example. It's not working as I expected.

When I run the example and choose an input channel and trigger source, the selection controls do not update with the value selected in the dropdown box. I can manually choose the input channel by entering "PXI-4462/ai0" but it chokes on the trigger selection unless I enter "OnboardClock" Since I need to synchonize my acquizition with an external trigger, this won't work for me. If I rename the card within MAX, the new name will show up in the dropdown lists, so I know it's getting picked up ok, but the choice will not update the selection controls. And entering anything having a board name reference in the trigger selection doesn't work; it will only accept "OnboardClock" with no board reference.

As far as I know I'm not doing anything out of the ordinary. I have a stepped sinosoid signal connected to AI0 and the trigger signal is connected to PFI0 (I'm trying to capture the level of the steps). I haven't modified the example in any way and the board tests out fine in MAX.

Is there anyone out there who can offer some help to me in getting this thing working?

Thanks!

Jesse

[Jonathan_S1]

Jesse,

Contrary to our other data acquisition devices, a DSA such as the 4462 must utilize an oversample clock, which is necessary for the delta sigma ADC architecture of the card.  You cannot supply an external sample clock. This clock can be exported to the PXI star trigger line and shared with other devices, such as DSA's, M Series, or E series cards.

This Knowledge Base gives a summary of this.

You can, however, provide a trigger that will start the acquisition.  If this is what you are looking to do, I'd recommend taking a look at the example "Acq-IntClk-DigRef.prj".

I hope this helps clear things up.

Jon

[jmevans]

Jon,

Yes, that helps quite a bit. It appears that I cannot use the 4462 in the way I want.

Jesse