Synchronized data delayed between two PXIe-4464 cards

[magnetsu]

All,

Could you please share any insight or thoughts on a data delay between two PXIe-4462 cards?  Both cards are in one measurement task through channel expansion, sampling at the same rate. One common signal is fed into Channel 0 in both cards. The screenshots below show the delay between the red and yellow traces. 

This article give a few options to address the issue. I thought the first option through channel expansion would work. 

Thanks,

XR

 

[dsb@NI]

Please attach your code. Also, what versions of DAQmx and LabVIEW are you running? Do you have two 4462 devices, two 4464 devices, or one of each?

[magnetsu]

Hi Doug,

I am using LabWindows 2017 with DAQmx version 19.1.1. I have two PXIe-4464 cards. Here is the code that I think is relevant: 

/* create the task */

DAQmxCreateTask ("", &probe_TH);

/* Setup the AI voltage channels using channel expansion. In total we have eight channels from two cards, four from each card. */

for (i = 0; i < MAX_4464_CHAN_NUM; i ++) {

      DAQmxCreateAIVoltageChan (probe_TH, (ch_info+i)->src, (ch_info+i)->name, DAQmx_Val_Diff, Vin_min, Vin_max, DAQmx_Val_Volts, NULL);
      DAQmxSetAICoupling (probe_TH, (ch_info+i)->src, DAQmx_Val_DC);
      DAQmxSetAIFilterDelayUnits (probe_TH, (ch_info+i)->src, DAQmx_Val_Seconds);
      DAQmxSetAIRemoveFilterDelay (probe_TH, (ch_info+i)->src, (bool32) 1);

}

Thanks,

XR

[magnetsu]

Sorry for the typo in the first post: there are only two PXIe-4464 cards, no PXIe-4462 card. 

[dsb@NI]

Here is what I see using the DSA Soft Front Panel:

The 4464 channels are added to the same analog input task. The synchronization is well within the interchannel phase mismatch for a single device. I see similar results when running the LabVIEW example: DAQmx\Analog Input\Voltage - Finite Input.vi

Given that the SFP and the LabVIEW example demonstrate synchronization via channel expansion and no explicit synchronization code, I recommend taking out code to remove filter delay.

>     DAQmxSetAIFilterDelayUnits (probe_TH, (ch_info+i)->src, DAQmx_Val_Seconds);
>     DAQmxSetAIRemoveFilterDelay (probe_TH, (ch_info+i)->src, (bool32) 1);