Ambient pressure O2 cell checking using bits of the Dolphin loop.

[Freeflow]

I had a flash of inspiration at work today, and I've just checked my theory.

I have a way of doing a linearity check on an O2 cell using bits of the Dolphin loop. You can't do a test to above 1 bar pO2 [you'd also need 100% O2 for that], but I have checked the pO2 against a cylinder fO2 of 40% and got 0.40 bar-bang on.

You need the supply reg, the inhale lung I haven't tried the exhale lung yet] the bung that comes with the Dolphin and you threw away when you fitted a pO2 gauge, the mouthpiece, inhale one way valve and hose, and the pO2 gauge. Rigging everything as standard, you blank off the scrubber connector with the blanking plug and then drain the loop by sucking all the air out of the exhale side of the mouthpiece [leave the valve shut, it makes it easier].

Then turn on the tank and check the meter against the cylinder fO2. The inhale valve will open before the lung is full, so you don't waste too much gas.

Pics below!