manometer accuracy

paulmars Posted By paulmars, Feb 12, 2018 at 11:21 PM

  1. paulmars

    paulmars
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    Feb 10, 2017
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    What is a good reasonable priced accurate manometer to measure my barometric damper?

    My furnace should be 0.025 and my flue should be -0.02. Looking at the gauges for sale i see accuracy (read
    inaccuracy) ratings that would make readings in the range that I need almost useless. Exp:

    0.3% of full scale 55.00wc (0.003x55=0.165) Does that mean that a reading of 0.02 could be off by as much as

    0.165?

    +/-0.3% of full scale 83.02 InH2O NKTECH NK-L3 (0.003x83.02=0.249)

    ±1.5% of full scale 4.00wc Dwyer 478A-0 (0.15x4=0.6)

    Am I doing something wrong here?


    tks,
    pa
     
  2. semipro

    semipro
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    If you're just looking for something to use once how about building one out of clear tubing, some water and food coloring. All that matters once its connected is the difference in height between the water level in each end of the tubing.
     
  3. brenndatomu

    brenndatomu
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    Dwyer Mark II model 25...$25-30 on fleabay
     
  4. paulmars

    paulmars
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  5. peakbagger

    peakbagger
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    I used to do large power plant size boiler testing on occasion and my go to manometer was clear vinyl tubing and food coloring. The trick is to mount the tube on a piece of plywood so its sloping at a shallow angle to accentuate the difference in the water levels. A draftsman's tee or dry wall tee makes good tool to mark reference lines on the plywood assuming it cut square. Nice thing about water manometer is there is no required calibration.
     
  6. paulmars

    paulmars
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    i had considered making a unit, but for 25$ that dwyer is available. I dont understand how a home made would be more accurate.
     
  7. brenndatomu

    brenndatomu
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    I tried the homemade one...didn't work...bought a Dwyer 25 and done.
     
  8. semipro

    semipro
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    I'm not sure how a tube filled with water doesn't work but at that price, I think I'd go with the Dwyer too.
     
  9. paulmars

    paulmars
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    dwyer mark II 25 +/-3% of FS 3.0 is 0.09

    so, if it read your pressure at 0.03, that could really be anywhere from -0.06 to 0.12 and fall within the specified accuracy of 3% FS. Now i really doubt that it would swing negative for a positive pressure, so we could effectively limit that range to 0.00001 to 0.12 which is still an awful large range.

    pa
     
  10. brenndatomu

    brenndatomu
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    Yeah, I couldn't believe it either...but it didn't work...at all.
     
  11. semipro

    semipro
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  12. brenndatomu

    brenndatomu
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    semipro likes this.
  13. semipro

    semipro
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    A column of water is pretty sensitive. Did the Dwyer work well? I'm guessing the pressure difference must have been really low.
     
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  14. brenndatomu

    brenndatomu
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    Yes, still using it everyday...I have it permanently mounted for my wood furnace chimney...always check it after every load, just to make sure everything is dialed in...I've caught the barometric damper sticking more than once this way.
    Well, many/most wood furnaces call for -0.04 to -0.06" WC column draft....so, yeah, needs to be very sensitive...I've heard of some that spec -0.02" as the minimum! !!!
     
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