gage fluid

[K-Star Automotive]

How can i tell what type of fliud my manometer is calibrated for??

I have a 36" dwyer that i want to use to measure air speed with.

On the top of the gage are the words inches of water using water. Inches of Mercury using Mercury. Am i to assume that this gage is for water???

I have marvel mysterery oil in it now and it seams real lazy.

Keith

[jfholm]

[color=#000000]Keith,
too me it sounds like it is calibrated for either water or mercury, but those are two entirely different readings. Measure the graduations and if they are exactly 1" apart from the major graduations then I would say water. MMO has a specific gravity less than water at 0.876 @ 60

[86rocco1]

Since it's calibrated for inches of mercury when filled with mercury, it will also read inches of water when filled with water.

[coulterracn]

You could use water with a few drops of food coloring.

My 36" Dwyer has printed on the upper well 'inches of water using .826 sp.gr. red oil' and the inch marks are about 1 3/16" apart

Ray

[jfholm]

Ray,
you are pretty darn close there. I calculated 1.211" so that 1 3/16 would be pretty close

John

[coulterracn]

Hey John,

Not bad for a WAG (wild ass guess). I used a 6 inch machinist rule and WAG. I never really noticed the marks were larger than 1 inch.

Ray

[jfholm]

Ray,
Will you do me a favor? If you have some dial calipers measure from bottom of one major graduation line to the bottom of the next major graduation line, i.e. 2" to 3" and tell me as close as possible what the measurement is.

I remeber that there was a discussion once before how to calculate the difference in fluids with different specific gravities and I may no be doing it correctly. One way I get 1.210" for yours and the other way I get 1.740" - I want to know which way is closest to what you actually measure.

Thanks,
John

[K-Star Automotive]

I measured mine and it's .910" from big line to big line.

[86rocco1]

[K-Star Automotive]

Thanks, Guys.
So can i use regular water with some food coloring. Or do i need distilled water??

K

[jfholm]

I would use distilled water. Here is a table for specific gravities
You will notice that sea water is heavier and would give a smaller reading between major graduations to equal 1"

Here is another table that compares pure water to tap water and gives their specific gravity

I also read that tap water varies from community to community depending on what they put in it to "purify" it and can be heavier than "pure" water.

But for the reasons Ed mentioned the graduations are the distance they are. I would use distilled water and food coloring. In my area the water is so hard that after it sits in a clear vessel for awhile and evaporates it leaves a white deposit and you do not want that in your manometer.

John

[86rocco1]

You can use regular water but distilled water's best because eventually regular water will leave mineral deposits inside the manometer; how long that take would depend on the amount of dissolved solids in your water

[coulterracn]

[K-Star Automotive]

Thanks again guys. I have well water and it has a bunch of junk in it . So that's why i figured distilled would be a better choice for me.


Keith

[slracer]

John & Ray, Remember what Ed just pointed out and measure the IDs of the tube and reservoir too. I thought that Ed also had a well drop correction spreadsheet somewhere, but I couldn't find it. That would determine the actual distance of the "1 inch" marks should be apart. -- Doug