[Date Prev][Date Next]
[Chronological]
[Thread]
[Top]
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
>
>
> __________________________________________________
> Do you Yahoo!?
> U2 on LAUNCH - Exclusive greatest hits videos
> http://launch.yahoo.com/u2