manometer accuracy

[paulmars]

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

[adnadeau]

You're on the right track, except +/-1.5% = 0.015 x 4" = 0.06" wc. I suggest you look at instruments with a full scale deflection closer to what you are trying to measure. For instance, a Dyer Magnehelic 2000-0 with a full scale of 0.50" wc & and an accuracy of +/-3% FS has an error of .03 x .5 = 0.015". I bought one of these on eBay a while back for $35. Also, Dyer will calibrate their instruments for a fee.

[paulmars]

great tip. that would be more accurate. I asked dwyer and they just suggested their 400$ digital high range unit that was not any more accurate. I hope their gauges are better then their customer service.

On their Magnehelic 2000 page i also see one that is 0.25-0-0.25" w.c. and another that is 0.125-0-0.125" w.c.

[paulmars]

see http://www.homerepairforum.com/forum...7897#post57897