[PSUBS-MAILIST] Source for a demand regulator

I think Phil's regulator design looks very good. It cannot be to difficult to build. I suppose a manufacturer of bellows can advise us on the subject. We would need "soft" bellows that react on small pressure changes. Many bellows are made to be used as flexible exhaustpipe connectors or things like that. Not excactly the kind of subtlelity we are looking for. The biggest problem is, I think, the tilt valve. The forse needed to actualy tilt the valve depends on the O2 pressure. By enlarging the lever on the valve the force needed to open the valve becomes less. But the tilting-angle also becomes less. I suppose we could not use a flexible O-ring seal for the purpose. It has to be some kind of hard seal that opens even if the angle is small.

Maybe it is an idea to use a simple barometer. Glue a magnet on the hand and an adjusttable magnetic switch on the dial. Even a small pressuredrop will result in activating the switch. The switch will activate an electrical valve. As mentioned before the disadvantage it that you will depend on electricity. On the other hand it is easy to ad a second magnetic switch that activates an alarm if the pressure drops to much. If you need to ad O2 manualy you can use the barometer to monitor what you are doing.