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Re: [PSUBS-MAILIST] co2 monitor source
please get me out of this mailist
----- Original Message -----
From: "Cliff Redus" <dr_redus@devtex.net>
To: <personal_submersibles@psubs.org>
Sent: Friday, November 08, 2002 10:57 AM
Subject: Re: [PSUBS-MAILIST] co2 monitor source
> Brent the Standard Air has 314 ppm of CO2 and ABS rules state that the
CO2
> level must be kept below 0.5% or 5000 ppm. In a closed cabin, without CO2
> scrubbing, CO2 level rises and cabin pressure drops. This gives you two
> options for using the CO2 monitor in a control strategy. Option 1, as you
> have noted, is to use the CO2 monitor to start the blower on the CO2
> scrubber when the CO2 ppm reaches a high CO2 set point. If you follow ABS
> rules, this would be some level less than 5000 ppm. The blower would
remain
> on shortly until the CO2 level drops below the High CO2 setpoint at which
> point it would cut the blower off i.e., the CO2 level would be controlled
> around this set point. Option 2, is to have the CO2 scrubber blower
> controlled not by CO2 ppm but with cabin pressure. IF a controller is
> monitoring the pressure and the pressure reaches the low pressure set
point,
> an O2 solenoid valve on an O2 tank (after being regulated down to say 150
> psig) opens to let O2 into the cabin. A needle valve can be used to set
the
> flowrate to say four times the O2 consumption rate. This raises the
pressure
> in the cabin until the upper pressure set point is reached at which time
the
> solenoid valve is closed. With this technique, the CO2 monitor is used to
> track the CO2 level only and its relay is wired to an alarm that would
> indicated if the CO2 absorbent was fully contaminated and not scrubbing.
> For option 2, a 0-2000 ppm sensor would be better since the control
strategy
> is maintaining the CO2 level indirectly near it level in standard air.
> Option 2 is a PLC and electronic sensor version of Phil Nuytten mechanical
> 1-atm. environmental control system. The problem with Option 1 is that it
> does not control the O2 level. You would have to have an O2 monitor and
> some method for setting the O2 flow rate into cabin. Many folks just use
a
> needle valves and feed in at the standard consumption rate.
>
> I prefer method 2 or the Nuytten mechanical method because they control
> both the Co2 and O2 automatically.
>
> Cliff
>
>
> ----- Original Message -----
> From: "Brent Shaw" <drydivenz@yahoo.com>
> To: <personal_submersibles@psubs.org>
> Sent: Thursday, November 07, 2002 6:11 PM
> Subject: [PSUBS-MAILIST] co2 monitor source
>
>
> > anyone interested in c02 monitors
> >
> > WWW.dcs-inc.net
> >
> > offers one for around the $250us mark with a build in
> > relay to open and close at a set point.
> >
> > Thought this would be good for kicking in a co2
> > scrubber automatically when co2 buildup gets to say
> > (abs-5000ppm?) 2500ppm?
> >
> > any thoughts?
> >
> > brent - nz
> >
> >
> > __________________________________________________
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>
>