I notice the bouncing when the process is down and no
Water is flowing through the flow meter.
Since this data has to be reported and when the process
is down the flow meter should read zero. It’s bouncing up to a positive number
and logging flow data when it shouldn’t.
I changed the filter setting on this particular analog input to
50hz and reduced the bouncing.
I appreciate all the help
Thanks
I am curious as to why changing the notch filter to 50Hz improved the noise rejection ?
Don't you guys over the pond use 60Hz mains frequency anymore ?
In class I always told my delegates to set the notch filter frequency to 50Hz for the UK, "for best immunity to noise generated by the mains wiring".
Anyway, don't rule out that the signal may be coming from the flow-meter itself, so you could test for this by substituting the flow-meter with a 4-20mA current source and running the process. If you still get bouncing you'll know it's wiring/cabling issues. If you don't, refer back to the flow-meter manufacturer.
EDIT : Are you confident that the flow-meter is installed correctly, to the manufacturers specifications ?
Most flow-meters I have used prefer to be in upwards vertical flow, and greater than a minimum distance, related to the pipe diameter, from a preceding bend.
Is there any entrained air or gas in the fluid ?
Have you actually proved there is no flow when the process is idle ?