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Noise on Counter Circuit

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#1 embayweather

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Posted 27 June 2013 - 01:23 PM

I have been using Labjack U3 and DAQFactory to measure rainfall. They are attached to a Casella tipping bucket rain gauge . It has worked well for months using the circuit as in http://labjack.com/s...-switch-closure, figure 1. Recently I have been getting a lot of spurious counts, of the order or anything up to 200 in a few seconds. I have put this down to electrical noise.
Is there any electronic way to filter this noise out, without affecting the resulting switch close from the reed switch inside the rain gauge?



#2 LabJack Support

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Posted 27 June 2013 - 03:51 PM

Do you know if it is noise or bounce? Noise might happen anytime, but bounce is where you get extra pulses only when the bucket tips. The link you provided talks about bounce. One quick thing to try is a stronger pull-up. The U3 has in internal 100k pull-up to 3.3V, but you can add a 4.7k pull-up to VS to more strongly hold the line high.

#3 embayweather

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Posted 01 July 2013 - 03:23 PM

Sorry for the delay in replying, work does get in the way sometime. I can certainly say that the extra counts are noise, occasionally with some 200 in less that 20 seconds on a bright , clear day with no rain. ALso it appears to be related to some of the electrical kit on my desk. One of the other computers or one of the back up hard drives. I have put in a capacitor and that seems to have stemmed the problem for now. Best wishes Mike

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