help with counter on USB 6009

[Gatto Mannaro]

Hi all, I've a DAQ USB6009 and a device with a reed, and I need to use the counter to measure the pulses form this device (with a max frequency of about 10 Hz)

I connected the device on the counter and on the ground, considering that the USB6009 is "at high level" and that it can measure just on decrease

The problem is that for each input the counter "measures" 4 or 5 counts (not stable).

It does not depend on the reed, I also did a test with a simple switch.

 

Any idea how to solve this trouble?

thank you alot

GM