6602 Two Digital Input Counters Synching

[TonyLM]

Hi,

I'm trying to set up a system that counts the edges of digital pulses coming in. I have two inputs but both are related so I need to be able to properly reference the time both signals are coming in to properly analyse the data. I'm using a 6602 and using a sample clock to determine the time between each pulse in the data from one source and another sample clock to determine the time between pulses in the second source but if I try to relate the two sources the positions change each time I restart the program because the sample clocks are not triggered to begin at the same time. I've tried using the daqmx trigger off a digital edge but its telling me it is not applicable to the task.

Aside from this the program works fine, the data appears as expected, just not properly referenced to each other. I just need it to always begin counting at the same time to properly reference one source to the other. I have seen many articles on multi device synching but can't find anything on counter synching between two counters in the one device.

Any help would be greatly appreciated.

[Tom O]

Hi Tony,

Have you seen the example at http://zone.ni.com/devzone/cda/epd/p/id/4836? It shows how to read from up to 8 counters using your board that are synchronised. This should do the trick for you, have a look and modify the program slightly to use only two counters.

Two things that the example does that I think were causing you problems:

• The counters are configured to work from the same timebase that is provided externally (for example, you could use a spare counter to provide this timebase). This is important in synchronising the counters
• The counters are all configured to use a digital edge as a trigger. Have a look at how this is done in the example; I'm not sure how you're trying to implement your trigger but the example should help.

I hope this helps you, good luck!

Best regards,

[TonyLM]

Hi Tom,

That example was pretty much exactly what I was looking for.

You've been a great help. Thanks very much.

All the Best,

Tony