u-tube manometer

[hubba]

I have been reading and have mixed feeling about it. when building one do you mark the inch marks as 1 or 2 inches. I have seen it done both ways on peoples homemade ones. just want to know what is correct.

[86rocco]

For every inch the fluid rises on one leg of the u-tube, it goes down the same amount on the opposite leg so if you're measuring on one leg only as is customary, marks one inch apart correspond to two inches of pressure difference.

[hubba]

ok thanks. so if you built one with one tube and a reservoir it would actual inches as marked?

[1960FL]

Yes that is correct as long as you understand the whole well drop thing and the need to minimize it by having a very large differential area ratio.

Rick