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[PSUBS-MAILIST] Oxygen sensors
There are many sensor manufacturers, but the best ones I have been able to find for gas mixing are the Maxtec (formerly Ceramatec) CAG-250's. See www.maxtec.com. For PSub application, you will need to find a way to mount at least two of these (independent verification) in a position where there is sufficient ambient airflow so that the reading does not become stagnant. One scheme that has been used in some models of rebreathers is to use three such sensors, the average of which is used to control the oxygen addition solenoid (0.21 ATA or whatever setpoint). If one reading should fall well outside the other two, then the input from that sensor is discarded (with a visual or audible warning), and the remaining two averaged to control the solenoid. In practice, I would use three sensors for a fully automated system. For manual oxygen addition, if you are monitoring the oxygen level diligently, it should be fairly easy to
keep PPO2 above 0.16 ATA, so you could get away with two, or even one if you trusted it enough. In the conceptual PSub design I've been playing with, all environmental controls (PLC controlled) are in series in a common loop, such that the ambient cabin air goes in an intake at the floor, is dehumidified, measured for oxygen content (These sensors are placed downstream of the dehumidifier to prolong the life of the sensors, but upstream of the scrubber, so as to get an accurate cabin oxygen fraction), supplemented with oxygen as neccesary, scrubbed, and then heated or cooled as appropriate, before being delivered to the cabin through high level vents.
-Sean
--Original Message Text---
From: Captain Nemo
Date: Wed, 2 Aug 2000 18:54:21 -0000
----- Original Message -----
From: Dale
To: Psubs
Sent: Wednesday, August 02, 2000 7:01 PM
what does everyone else use???
dale
Yeah, I wanna ask the same question. I haven't thought about this for a while, so I'm at a loss for manufacturers and suppliers these days. Can anyone (Vance? Phil?) tell me where I can buy an oxygen sensor / supply system? (A sensor that would measure the level of oxygen in the cockpit mix, and an automatic valve that would replace depleted oxygen to keep the mix normal?)
It's a little worrysome fan-forcing the compartment atmosphere through a gym-sock full of Sodasorb, and hand-valving a shot of O2 into the mix every so often by guesswork, and I'd really like a commercial setup.
Thanks
Pat