NI USB 6008 problems with edge counting

[suksunh]

I got a NI usb 6008 DAQ card. Vi example Count Digital Events.vi was called to acqure encoder reading. It gave error message like that "Error -200077 occurred at Property Node DAQmx Channel (arg 2) in DAQmx Create Channel (CI-Count Edges).vi->Count Digital Events.vi Possible reason(s): Requested value is not a supported value for this property.

Property: CI.CountEdges.ActiveEdge
You Have Requested: Rising
You Can Select: Falling

Channel Name: Dev3/ctr0

Task Name: _unnamedTask<5>

"

Does anyone have the vi program or any advice to make it run to acquire encoder reading? Thank you very much!

Best regards,

suksun

[Tom_W_[DE]]

Hi Suksun-

As the error text and this KB suggest, you will need to select "Falling" as your active edge for counting.  The USB-6008 counter only supports falling edge counting.  You can select the active edge by using the "Edge" input to the DAQmx Create Virtual Channel VI in the example you're using.

Hopefully this helps-

[suksunh]

Hi Tom W,

         Thank you very much.

     Suksun

[breneliere-r]

Helo,

I got a NI usb 6008 DAQ, I want to use the counter  to count the impulses of the optical sensor of the rotation motor. I don't know how to put value in a buffer all to one seconde, and how to display this on a graphic.

thank to your assistance

[Tom_W_[DE]]

Hi breneliere-r-

The USB-6008 does not have the capability to perform buffered event counting so you will not be able to sample in one second intervals with hardware-timed accuracy.  You should be able to, however, achieve relatively good accuracy by simply starting a software-timed task and then reading repeatedly in a loop with a one second software delay per iteration.

You don't mention which development environment you're using, but the Count Digital Events examples in LabVIEW (Help>>Find Examples...Hardware Input and Output>>DAQmx>>Counter Measurements) or for ANSI C (Program Files\National Instruments\NI-DAQ\Examples\DAQmx ANSI C Examples) should give you a good starting point.

Hopefully this helps-