strip noise

[bassinbc]

I would like to strip off noise from a 10V pulse. The hardware I am using is cdaq 9172 with 9205 Module. I feed in a 10V pulse that varies in frequency. The output goes to an indicator to indicate the frequency. The problem is that there is a 4.3k noise of a small magnitude riding on the pulse. So at zero frequency the indicator picks up the noise and reads 4.3 kHz. When I generate a frequency the indication is correct, it is just a zero I read the noise. How can I strip off the noise from the pulse. In the attached VI I used a SINAD analyzer to get rid of the noise but I also limit my output to 3k with this method.

[Ben]

paraphrasing Ott* "The most effective method of eliminating noise in an electronic system is at its source."

Are you sure that the noise you are seeing is not "ringing" due to an impeadence mis-match?

A notch filter set for 4.3KHz should help.

Ben

*Author of Noise reduction Techniques in Electronic Systems"

[johnsold]

I read the same books as Ben and agree with his statement.

If you only want the frequency of the 10 V pulse, try a threshold comparison on the signal with the threshold set to abut 5 V.  If the 4.3 kHz signal has low amplitude, you should be able to reject it by creating a binary signal.

Lynn