Counter counts twice as many edges as it should, but the correct frequency. Why?

Hello world

I use a PCI-6122 (series S, DAQ - STC) and Labview 7.1 on a Windows XP.  There are only two counters on this card (0 and Ctr 1 Ctr) and I need to use both of them to count the edges.  While testing meters, I am inputing a TTL signal to 10 kHz at the door of each counter, to be used as an external sample clock, and a 20 Hz TTL signal in each counter, to serve as input signal Source.  CTR 0 account 40 edges per second, i.e. twice as much as it should, while the Ctr 1 reads the correct number of edges, i.e. 20 edges per second.

The strange thing is that when I switch the connections of the portal and Source for two meters to measure the frequency (or period), two meter to read the correct frequency, i.e. 20 Hz.  To the best of my knowledge, the two counters have been reading of the
correct the number of edges a couple of weeks.  Also, I have reset the
device several times but it doesn't make a difference.  I'm trying to understand why this is happening and how to fix it, but I'm not about to answer each question.  Does anyone have any suggestions?

Thank you.

After many tests on mine, and talked with an engineer of NOR and repeat tests by telephone, it seems that there is something wrong with the meter (a) on the Board of Directors.  I sent it for repair (luckily it was still under warranty .)

Tags: NI Hardware

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