Manometer advice

[Old Grey]

I am working with manometers right now.

The U-tube that was on this bench was designed for water, and that makes each 1" H2O equal to only ½" on the scale.

I'm used to SF benches that have reservoirs and oil of specific density less than water, and that makes the space between inches H20 closer to 1.2".

For me it's easier to get greater accuracy with 1.2" spaces rather than than ½" spaces so I'm going with the reservoir.



There is a lot written in this forum about manometers and I think the general consensus was to use 3/16" tube, because the smaller 1/8" reacted too slowly, so that's another area you may have to look in to.

I'm also thinking about MMO and was wondering if anyone knows if MMO stains clear PVC tube?

[slufkin]

I made some progress with my bench, tried to upload a pic from iPhone but it is too big.
Anyways, time for a dumb question, I have my inclined monometer built and I understand how to use the scale generator but I'm not clear on one aspect. Is it best to place the reservoir low mod have zero at the bottom of the slope or place the reservoir high and have zero be the top of the slope? Does the question make sense??
Thanks for your help guys.

[slufkin]

I think I got the picture to load.

flowbench4.jpg

[Brucepts]

Looks good!

Won't matter if it rises or falls, comes down to personal preference.

[jfholm]

Looks good!

Won't matter if it rises or falls, comes down to personal preference.

As Bruce said it does not matter if it rises or falls. I ended up making mine fall and the only reason was when I had it rise and then you turned off the flow then some of the fluid would stay up in the tube. I think part of the reason was I was only using 1/8" i.d.tubing. You can also put a few drops of dishwasher rinsing agent in your water so it does not cling. I never tried that though. As for accuracy it was the same either direction.

John

[slufkin]

Got some more work done, but I'm getting more frustrated than a 3 legged dog trying to bury a turd on a frozen lake.

Could anyone tell me how it is even possible for my manometer to look like this when the vacuum is turned off and has been for days???
I even added onto the "Open" tube so that it hangs down to the same distance from the floor as my "Sampling" tube....thinking maybe it was showing me the difference in air pressure from the difference in height.... No dice.

[Brucepts]

check for fluid down stream stuck in your line

[Tony]

And check for trapped air bubbles.
With no pressure appled, there will be the same resting "weight" of fluid in each leg.
But there could be a big bubble lurking somewhere hidden down in the leg that is sitting up high.

The air lines should have no fluid traps, and the fluid lines no air bubbles.

[slufkin]

Thanks guys, I will have a closer look.
Does this mean I haven't accidentally discovered a zero gravity machine.?.?

I better call NASA and let them know.

[jfholm]

One thing I would also suggest trying is some of that anti-spotting agent for dishwashers. It causes the water to sheet off and not stick. I helps the water to not stick in your tubes.

John