I do believe you're wrong.USMCVet wrote: ↑Sun Feb 25, 2018 12:48 amSo we have a basic manometer which is U shaped and symmetrical. We fill it with water. At this time I see it like a scale. You have equal atmospheric pressure on either side because diameter of tubing is the same which means the amount of water on each side is the same. So both sides being equal you can apply a steady pressure to either side and get the same result. However if you have the same tubing on either side but a lot more water on one side which equals more weight for atmospheric pressure to fight you won't get the same result if you add the atmospheric pressure to either side.
If you have a lot more pressure on one side (side with more water which weighs more then air) then the other then the scales aren't equal.
Take your basic idea, put a gallon bucket on one side, with a 1/8th" tube coming off the bottom, and up the side. you've now created your manometer with unequal size tubing.
what's gonna happen when you put 10cm/h2o pressure on one side or the other?
how're you gonna get water into the cpap? how're you gonna keep water from blowing OUT of the cpap into the big container.
Your dog bowl example works by the water pulling a vacuum in the sealed bottles, which holds the water up in those, then when it gets too low, there's enough room for bubbles to enter the lower opening and release some of the vacuum, thus releasing water.
This works well, because it's a static system, no pressure variances.
I'm not saying that doing it with the varying pressures of cpap would be impossible, but it's going to be much harder to engineer reliably. Basically, if this was *easy*, it'd already be widespread... among the small percentage of people that need it.
Someone did do something similar in the past, but it involved, (iirc) multiple tubes, a large sealed jug, and precise height control between the cpap and the auxiliary jug to make it work.
An alternative would be to put a time of flight sensor in the top of the water reservoir, and a peristaltic pump to refill the chamber automatically.... but $$$