What??? I never mentioned the car's oxygen sensor....you did. I was saying that the control algorithms behind the cruise control are much more responsive than a solenoid controller in an eCCR unit. I wasn't talking about oxygen sensors being used in cruise control at all. You're off base here, buddy....it's not what I was talking about in the slightest.
In a control system, you have measured process variables (inputs), desired setpoints, and control elements. I was comparing process variables of two systems, not oxygen sensors.
This is one of the more absurd thread diversions I have seen on SB.
The time scales, precision requirements and sensor fidelity of the cruise control example are so different to those of a rebreather as to be less than helpful.
The controller (manual or electronic) in a rebreather has to maintain the set point at a reasonable approximation of the target. This is required first to avoid the diver passing out, then as a secondary concern an oxtox and way down the list to optimise deco...
Let's say we are at 30m with a set point of 1.2. We need a FO2 of 30%. With a loop volume of say 5l that is 1.5l of O2 under pressure so 6l surface equivalent. To avoid hypoxia we want to stay over a ppO2 of 0.16, so FO2 of .04 or 0.8l. That leaves 5.2l available to metabolise before a proper problem. About 5 minutes.
Look at an ascent. Say we get from 30m to the surface in 1 minute to make it harder for the controller. At the start there is 6l of o2, 1l will be metabolised over the course of the ascent, some will be lost as it is dumped to maintain buoyancy.
After 20 seconds (at 20m) the lungs will have expanded to by 4/3 so we loose 1/4 of the gas, or 1.5l of O2, and metabolise .33l so we have 6-1.83= 4.17left at 3 bar so 4.17/15 free gas loop volume) or 27ish%. Still conscious.
Next 20 seconds, to 10m. The lungs expand by 3/2 so we loose 1/3 of the remaining 4.17 so we have about 2.8 left, less about .33 metabolised leaves about 2.5l in 10 or 25ish%. Still able to see, hear and press buttons.
Last 20 seconds, now we are down to 1.25-.33 = .92l so ppo2 is .92/5 = 0.184 so still good.
It looks like the controller could wake up once a minute and still maintain a breathable loop. That is why people can be the controller and live.
Interestingly a slower, more normal ascent is more of a danger for hypoxia as a greater proportion will be metabolised. If no O2 is added then passing out is to be expected. On the other hand it is dumped more slowly so the polling interval of the controller does not need to be faster.
The real issue is not controlling the gas in, it is having any idea as to the current loop composition due to old or broken cells.
