Building a Manometer

[Luis H]

I have gotten a magnehellic guage on the bay but I also used a DIY one out of tubing that works just fine. The whole point of a DIY project is to do it yourself so i think you should make one just for the knowlege and satisfaction gained. Then you can use it to amaze your buddies who will think you are a genius.

Yeah…IMO, the “U” tube does have a cool factor to it.

You can also use the a “U” tube manometer to compare the values from a Magnehelic.
Personally I have always been pleased with the readings on a Magnehelic.

The visual effect of a U tube is always good.

 

[c-snake]

For example if it is exactly twice the area that means that if the fluid in the small tube goes up by an inch, the fluid in the large tube will go down by ½ inch. You still need to read both sides for a total of 1.5 inWC. The error would be too much if you ignore the larger tube.

Again, you can only ignore the large side if it is many times larger than the smaller tube.

OK, that makes sense, but there must be a formula that will give the size of the larger tube to give a direct reading in inches on the smaller tube, no?

Do you guys find it difficult to read the u-tube guage with just a single sized tube?
How are you positioning your scale?

This link shows a cool manometer reading explanation.

Gas Laws: Pressure

 

[Camerone]

Do you guys find it difficult to read the u-tube guage with just a single sized tube?
How are you positioning your scale?

I got two very cheap metal rulers at Harbor Freight, and I set them up so that they're end to end (as in, the zeros are aligned.) They're tacked vertically on the support piece for the U. I fill the U tube with enough water, plus a drop of food coloring to make it easier to see, and fill the tube so that it starts out just level at the zero point where the rulers meet.

Then it's easy enough to just read the single scale and multiply by two.

The most expensive and time consuming part of this was the rulers - I think they ran $0.99 for the pair, if I recall... and the whole thing is like a 10 minute project. The rest is scrap lying around the garage; I just re-did my kitchen, so I had lots of cut-off wood for the base and the upright.

It worked great for quite a while, but I ended up buying a surplus Magnehelic for $20, and, while likely not nearly as accurate, it is a lot more convenient and gets the job done. I paid more for the fittings to put the hoses and mouthpiece on the Magnehelic, though, than the entire manometer...of course, that's still not saying very much.