USB-6009 AI and AO

[Blokk]

Hello,

I have an USB-6009 DAQmx device. I would like to measure analogue input with the possible highest sampling rate (48kHz) . At the same time, I need to ramp a voltage analogue output from 0 to 5 Volts, lets say during 2 minutes. These two tasks do not require close syncing. Regarding to the spec, the highest rate of the AO is 150 Hz. It is ok for my application.

So the AI measurement will use device internal clock, and the AO can only work with software timing. Is it possible to independently ramping the voltage output and at the same time, reading the analogue input? If not, is there a workaround for this device?

Thanks for advice!

Regards,

[Blokk]

I have made a test version (the final solution will do measurement for 2 minutes, so I will need to ramp up the analogue signal from 0 to 5 Volts in 2 minutes, and I think 10 msec will give a sufficiently smooth ramp curve --> 24000 steps over the 5V range).

In this test VI I do measurement on two analogue inputs using internal timing, and in parallel, I do the ramp signal with software timing (I guess it is not advised to go below 10 msec because Windows can slow down too much?).

Additional question: when I use DAQ on the two input channels, I understand that, the available highest rate is half of the maximum. But when I plot the two channels, the points are at the same time on the XY graph. How does  LabView interleave data from the two channels during measurement?

Thanks for help and advice,

Regards,

[Andrea_Perin · Accepted solution]

HI Blook,

your test VI looks ok. Of course , since the AO is in SW timing and you are running it on a Windows platform maybe you will see some jitter on the output . But you said, you don´t need a thight sync, so it shouldn´t be matter.

For what concerns the way LV manages the data acquired from a multiplexed DAQ card you have to keep in mind 

that the waveform timestamp is generated from the driver on the PC and not directly on the card. That means that even if the sample of two channels are acquired in two different 

moments (as you supposed separated by the settling time of the ADC) this will be transparent for the SW and they will be considered as acquired exactly at the same moment.

National Isntrumetns also offers simultaneous sampled acquisition card (and not multiplexed) to overcome this issue.

Best regards

andre

[Blokk]

Thanks very much for the useful info 🙂

May I have another question regarding to DAQmx drivers? (I know I should open a separate post for this officially)

I wonder if it is possible to make "on-the-fly" calculations on the USB-6009 board? For example: I collect data using the onboard timing with 24kHz, but I do not want to push all this data into my TDMS file. Instead, I would like to do some Point-by-point Mean calculation, and only write out this moving average at every 100th point. So with this I would have a nice statistics, beside a  not too large file (I always like to avoid post-processing of data).

Is the above scenario possible in LabView (with this USB-6009 board).

Thanks very much,

Best Regards,

[Andrea_Perin]

No, the card cannot do it. There other platforms as the NI R series card with FPGA chis on which you can integrate intelligence for onboard data processing.

On a 6009 it is not possible.

Best regards

Andrea

[Blokk]

Thanks!