ni 6008 wrong counts

[Jochen48]

I use a ni 6008 device, to count TTL-Signalls from a descrete particle counter.

99% of the time, the ni 6008 counts are correct and the same as the particle counter, but sometimes I receive wrong counts from the ni6008.

The NI 6008 counts much more events, than the particle counter.

I suspect static electricity as a cause. The particle counter ist conected to the mains, the laptop works on batterie. the line between particle counter

and the NI 6008 is shielded.

Is there a solution for my problem?

Thank You

Jochen

[Christoph_D · Accepted solution]

Hi Jochen,

if you count too much edges it is probably due to some noise or bouncing in your signal. You would need a appropriate digital filter that limits the minimal pulse time.

In the following article you find a small example on how to set the digital filter (although it is a different DAQmx HW):

Community: Using DAQmx Counter Digital Debounce Filter with 660x Family - National Instruments
https://decibel.ni.com/content/docs/DOC-3766

But the USB-6008 does not feature digital filtering, so you probably need another device or you have to add external filtering.

To really confirm my analysis you would have to look at the signal in a oscilloscope and you should probably detect very short pulses.

Best regards,

Christoph