PCLe-6321 Counter remains 0 when edge counting with 15MHz edge source

[HugoChu]

I use PCLe-6321 for edge counting, and I just use Test Panels in NI- MAX, the Counter works fine first, but when I change the source frequency to 15MHz, the counter value always remains 0. Specially when I change the frequency to 20MHz or even 30MHz, the value changes. Does anyone know the reason?

[HugoChu · Accepted solution]

Sorry, everyone, it turns out to be an issue of signal interference from the splitter connected to the signal generator. I use the signal generator to generate a square wave as the counter source, and use a splitter to get 2 lines, one connected to 6321, another connected to an oscilloscope to observe to signal. When change the frequency of square wave to 15MHz, somehow the signal transmitted to 6321 will be influenced and be lower, not enough to trigger counter to add, so the value always remains 0. When I disassemble the splitter and use only one line, the counter works.