refresh rate of the daq-pad 6016

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Hello everybody,

I am using a DAQ 6016 and 2 DAQ 6009. My problem is that the refresh rate of the 6016 is very slow if I put two analogic channels to read.
I asked for a sampling rate of 20KHz and 25 samples for both channels, which should last only 1.25ms each. The samples are fine, but the graphs or the values refresh only less of 5fps. In the same time, if I run the DAQ6009 with the same configuration, it refresh faster. If I put more channels, the 6009 refresh stay more or less the same, but with 7 channels the 6016 refresh 1 time every 1 or 2 seconds.

An other test was: 400Hz +-10V to one analogic input, and I just asked for a single point in a loop. The chart couldn't allow me to see the 400Hz, so the equivalent sampling should be at least more than 10S/s.
I could also see that it sampling wasn't steady.

I use a P3 900 MHz as computer with 512MB RAM, USB 1.1, and tried on a P4 1.8GHz, 512 MB and USB2.0 for the same results.

Does someone see what could be the problem?

Greetings
Laurent

[Abhinav T]

Hi Laurent,

It is difficult to narrow down your issue without having a glimpse at your code. Would it be possible for you to post a screenshot of your code or the LabVIEW code itself?

Thanks,

Abhinav T.
Applications Engineer
National Instruments

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thank you for replying, abhinav T

I link here a screenshot of the most basic program:
    10 samples at 10KHz for both of the DAQ assistants, with make the acquisition of aio of the 6016

the displays refresh something like 4 times per second, whereas one acquisition should last 1ms.

On the other hand, i tried to emit one bit and mesure the time up to its reception (I linked 2 hardware channels together). Almost each time, I have a delay of 15ms



Any idea what could it be? I already ran 2 times the autocalibration

Laurent

[Abhinav T]

Laurent,

Is there any reason why you're using 2 DAQ Assistants?

Can you try using a single DAQ Assistant instead or one of the example programs in the NI Example Finder (Help >> Find Examples...)?

Abhinav T.
Applications Engineer
National Instruments

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hum, well, the reason is just that I didn't realise it was possible... I belived it would make an error. Whatever, thank you very much for that, because you just helped me for another problem
But for the refresh problem, it seems that the 6016 prefer 1000 samples at 100KHz than 10 samples at 1000 Hz. Is there a way ti find the optimised frequency and rate?

Laurent

[Abhinav T]

Laurent,

I have tested the DAQpad-6016 at the settings you described and everything works fine. Can you try acquiring one waveform using the configuration in the image attached, (just measure one channel at 1kHz and acquire 100 samples per channel)?

Thanks,

Abhinav T.
Applications Engineer
National Instruments

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I just tried it: the acquisition in continuous is fine, but if i select "n samples", it's jerked.
I tried with 10 channels 20k and 256 samples each, it's ok too, but only in continuous. In n samples, it's the same problem.

Laurent

[Abhinav T]

Laurent,

This is expected behaviour, the continuous acquisition mode maintains a constant data stream from your device. The N samples mode is only meant to be run once, if you place that in a while loop, it resets the driver everytime you start, stop and restart the acquistion, this can lead to a lag between acquisitions. For your application, I would recommend the continuous sampling mode as it ensures that you do not lose any data in every iteration of the while loop.

Abhinav T
Applications Engineer
National Instruments

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The time taken to refresh the value is so long, it's too bad. Now, I got another problem: if I try in continuous mode, the DAQ freeze after some time, or make my pc bug. The result is: I cannot access to the daq, but the program is still accessible. And each time, even if I force to close Labview, I finally have to reboot the PC

May be it should be better to begin by the beginning: I have to realise some operations on 400Hz signals, with a refresh as fast as possible, and to control an output in the same time. I got some operation like a proportionnal controller to realize, and I would like to know if the daq could do that with a reaction time <100ms.

For the moment, it's ok, but the reaction time is >1s in "n samples"
In "continuous", the reaction time is less, but not really really cool, and it finally crash

What could be the best configuration for the best response?

Thank you

Laurent

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Do I need to open a new thread for the crash of the DAQ6016 in continuous mode?