adccommunitymod (AutomationDirect) asked a question.
Created Date: January 29,2010
Created By: sii
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I have two AD pressure transducers in a vacuum line leasuring vacuum pressure on both side of an air filter. I am able to accurately (at least enough for my purposes) measure the pressure at both locations. I would also like to use this data to derive a differential pressure across the filter. I have tried couple of different ways and seem to have the same problem either way. 1) I tried subtracting the raw 0-4095 inlet pressure from the 0-4095 outlet pressure and it works fine after the filter has begun to plug a little bit. Howver with a new filter in the chamber, occasionally the calculated value will jump to 9999 or 9998. I am guessing this is simply because the sensors "bounce " a little bit and occassionally the inlet sensor reads a slightly higher value than the outlet sensor. 2) I tried doing my math with the values scaled by the ANLGIN I-box with the same result. This really is not a problem except that I have a meter on the C-More that is reading this differential pressure and it just constantly spikes between min and max. Anyone have any words of advice here? TIA
Created Date: January 29,2010
Created by: sii
I guess my thinking is that IN THEORY the reading from the inlet sensor can never be greater than the reading from the outlet sensor. I don't need the negative but I think I could
.........input P> output P.....LD
KO
so that the negative number is never allowed to go to the final Vmem.
Right?
Created Date: January 29,2010
Created by: bfitz
I guess my thinking is that IN THEORY the reading from the inlet sensor can never be greater than the reading from the outlet sensor. I don't need the negative but I think I could
.........input P> output P.....LD
KO
so that the negative number is never allowed to go to the final Vmem.
Right?
That's how I would probably handle the situation. You might also try adding some filtering to both inputs. It might settle the noise a little and prevent these momentary bounces. Note that filtering introduces its own set of issues though.
Brian
Created Date: January 29,2010
Created by: sii
Great...I'll give this a try tonight. Thanks to all.
Created Date: January 30,2010
Created by: sii
That worked great....many thanks.
Created Date: January 29,2010
Created by: sii
I have two AD pressure transducers in a vacuum line leasuring vacuum pressure on both side of an air filter. I am able to accurately (at least enough for my purposes) measure the pressure at both locations.
I would also like to use this data to derive a differential pressure across the filter. I have tried couple of different ways and seem to have the same problem either way.
1) I tried subtracting the raw 0-4095 inlet pressure from the 0-4095 outlet pressure and it works fine after the filter has begun to plug a little bit. Howver with a new filter in the chamber, occasionally the calculated value will jump to 9999 or 9998. I am guessing this is simply because the sensors "bounce " a little bit and occassionally the inlet sensor reads a slightly higher value than the outlet sensor.
2) I tried doing my math with the values scaled by the ANLGIN I-box with the same result.
This really is not a problem except that I have a meter on the C-More that is reading this differential pressure and it just constantly spikes between min and max.
Anyone have any words of advice here? TIA