Can i use USB 6002 to achieve buffered event counting?

[xi438172@ucf.edu]

Hi,

I use the PFI0 as counter input(count edges). Do i need a sample clock as gate signal? Can i use internal signal as the source of sample clock? Because I only have the USB 6002 device. I refer to the usb6002 Specifications, it only have 1 counter.

Thank you.

[ZYOng]

You can use a dummy AI task to generate the sample clock. See method 2 in Synchronizing Two Counter Tasks in NI-DAQmx

[xi438172@ucf.edu]

Hi,

Thank you so much for your help. I tryed it like that. But there's an error as shown in the figure attached. Maybe is there something wrong with the code I wrote?

[Kevin_Price]

Unfortunately, your device isn't capable of this kind of task.  The USB-6002 has only a single counter and it can only be used for "On Demand" edge counting.  No hardware sample timing is supported.

The only workaround I can offer is to feed the pulse train signal in as one of the channels in an AI task and sample fast enough to catch all edges of interest.  With a 50% duty cycle, I'd aim for at least 4x the pulse rate to give you 2 nominal samples per high time and low time of the pulse.  For any other duty cycle, I'd increase the sample rate to aim for 2 samples within the time of whichever digital state is shorter.  Then you'll need to post-process the AI data to find and count the edges.

-Kevin P

[xi438172@ucf.edu]

Hi Kevin,

Thanks for your responding. Can I use pulse trigger to achieve edge counting periodically in USB-6002 without external signal as trigger source?

[Kevin_Price]

Sorry, I don't understand exactly what you're asking.  My best guess is that no, you can't, and you're still looking for a way to get your device to do something it simply doesn't support.

Can you sketch up a timing diagram of your signals and describe the measurement you're looking to do in more detail?

-Kevin P