What is the resolution on the NI PCI-6030E frequency counter?

[cjro]

I'm using the NI PCI-6030E and I'm trying to get a reading of a sine wave with a frequency of 1kHz.  The input signal is very strong and accurate (network analyzer showed it is outputting a frequency within a few millihertz of 1kHz) but when I hook up the DAQ to the computer and use SignalExpress to test measuring the frequency of the input signal, the signal is much messier.  The input terminals are setup correctly plugged into PFI8 and ground and I'm using the 2 counter high frequency measurement method.  The signal that the DAQ is reading shows 1kHz plus or minus 10Hz even though the network analyzer is showing a much more accurate signal.  I have tried to change the measurement time from 1ms to 1s and the values do not get any better.   Using the 2 counter large range measurement method, the results are much more stable, but still fluctuate between an error of 5Hz to 10Hz.  Have I simply reached the resolution limit of the DAQ that I am using or have I not accounted for something to increase my resolution?

Thanks

[ManLongAtNI]

Hello cjro,

Keep in mind that counters are designed to measure the frequency of digital signals, ideally ttl signals. The unknown frequency of the unknown signal is calculated as a frequency of the timebase/number of edges during 1 unknown period. These edges are not as apparent on analog signals. To measure the frequency of your analog signal I recommend acquiring the signal then running a FFT.

Hope this helps.