I'm getting inaccurate results from my USB-6210 edge counting check from MAX. I have a TTL source that generates four pulses that is connect to PFI0 through a simple RC filter (390 ohm and 0.02uF). I start the edge counting from the test panel in MAX choosing PFI0 as the edge source. When I trigger my four pulses I receive a much larger count (sometime up to 20 counts) from the MAX test panel. Only when I remove the RC filter do I receive an accurate count (4 pulses exactly). I need to use the RC to filter out some 45KHz noise generated by another piece of equipment in the lab. I know I can set up the USB-6210 to use a time-based filter but I thought a simple RC filter would be a quick solution.
I have tried this with a USB-6211 with the same results. Only the USB-6009 preformed as expected with accurate counts. The USB-6009 edge count is not affected by the RC filter.
Any thoughts?
Thanks,