U-tube scale compensation

[01z28auto]

Hi guys,not sure if this is where this question belongs but here goes. I want to use MMO as my gage fluid in my u-tube manometer.
My question is what is the proper way to compensate for the sg of the MMO? I've read on here that it's 1/sg=1"wc. I've also seen it
questioned whether it's 1-sg+1=1"wc. The first method yields 1.1415" and the second yields 1.124. Which is the correct method?
I've got a cnc shop so I want to make a custom scale from some spare aluminum. Lastly,does this same compensation need to be
done on a u-tube for a velocity probe as well?
Thanks in advance!

[jfholm]

Hi guys,not sure if this is where this question belongs but here goes. I want to use MMO as my gage fluid in my u-tube manometer.
My question is what is the proper way to compensate for the sg of the MMO? I've read on here that it's 1/sg=1"wc. I've also seen it
questioned whether it's 1-sg+1=1"wc. The first method yields 1.1415" and the second yields 1.124. Which is the correct method?
I've got a cnc shop so I want to make a custom scale from some spare aluminum. Lastly,does this same compensation need to be
done on a u-tube for a velocity probe as well?
Thanks in advance!

I do not know if you have the MSDS sheet for MMO so I have attached it. It shows a specific gravity of .876 so it is lighter than water and you are going the right direction. I have always gone with the 1.1416" number. It would be nice to know as the error for only one inch is small .017 but accumulative for 28" that would be .476" difference between the two methods

what ever the correction factor you use has to be used for everything. Since the MMO is lighter it will react by going further up the scale than water at the same pressure. All the calculations we use are centered around inches of water.

John

[01z28auto]

John

Thanks for the help. I do have the msds for MMO. I guess my best bet will probably be to build a water u-tube and an MMO u-tube and see the exact difference. I can machine both correction factors on my aluminum,one on each side and try both out and come to my conclusion. If anyone has anymore to add,it would be greatly appreciated. Thanks again!

Paul

[jfholm]

John

Thanks for the help. I do have the msds for MMO. I guess my best bet will probably be to build a water u-tube and an MMO u-tube and see the exact difference. I can machine both correction factors on my aluminum,one on each side and try both out and come to my conclusion. If anyone has anymore to add,it would be greatly appreciated. Thanks again!

Paul

Paul,
we had quite the discussion on this very same thing a couple of years ago and I don't really think there was any resolve. I think your Idea is a good one but will take some effort on your part. build two vertical manometers tee'd into the same source. Just use a rule for one and put water in it. Then stop at every inch on the water one and measure the MMO one and that will give the answer I would think.

We even discussed different liquids and their advantages or disadvantages. Beer even came up, but I suggested to drink the beer first so it was not wasted and then use the urine that was produced

[01z28auto]

John

I read that discussion,hence where my question stemmed from. I'm not afraid of the work it would take,if I were i dont believe i'd be building a bench,lol. This airflow addiction sure does have a way of snowballing doesn't it? Just when I think I have one problem figured out,I find 2 more. When I find the answers i'm looking for,there's a then followed by ,I should've thought of that.

Paul

[1960FL]

specific gravity is a ratio against the standard or water +/- 1 so MMO is .876 or sg = .876/1 the ratio. the inverse is 1/.876 or 1.142 so i would start by believing that 1.142" of MMO = 1" of H2o.....

http://en.wikipedia.org/wiki/Specific_gravity


Rick.

[jfholm]

Thanks Rick,
That is the way I have felt. Thanks for your input. But don't you think he should go out to the ten thousandths? He did say he had a CNC shop. You know us old machinist. btw some time I will tell you the joke about the machinist and the parrot

[01z28auto]

John

It'll be programmed to the ten thousandth,but we'll find out where it cuts to.
I hope I didn't seem like I was touting the cnc acronym. I know a good machinist
can make just as quality of part with a manual machine as cnc. I still use the old
stuff daily,just lots more labor intensive of course. Btw,I'd love to hear about the
machinist and the parrot sometime.

Paul

[Brucepts]

John

It'll be programmed to the ten thousandth,but we'll find out where it cuts to.
I hope I didn't seem like I was touting the cnc acronym. I know a good machinist
can make just as quality of part with a manual machine as cnc. I still use the old
stuff daily,just lots more labor intensive of course. Btw,I'd love to hear about the
machinist and the parrot sometime.

Paul

Think it was an inside "dig" on Rick, he likes to go 8 decimal places on some things . . .



It's not a bad thing

[1960FL]

Hey i just know that if in my mind i shoot for .0005 I might be able to hold .002

Rick