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Re: [PSUBS-MAILIST] O2 & CO2 sensors
Hey Cliff,
Just had a primitive thought... Do you really "need" a CO2
sensor? Many of the CO2 scrubbing products available use colored
indicators which will allow you to see if the material has been
exhausted. Wouldn't a positive air flow indicator on the scrubber work as
well? If you know that cabin air is flowing through the material and the
material is still active, couldn't you assume that the CO2 is being dealt
with?
I do not use a scrubber on my sub, just SAR, surface and
replenish. However, my biggest fear would be from excess O2 or from
overpressurization of the cabin. Excess O2 levels can be a fire hazard
(remember NASA's problem). And, if for some reason, the inside of the sub
had to be pressurized with a high O2 concentration, it could be toxic to
the occupant. The O2 sensor could warn you of this danger and a barometer
could warn against excess cabin pressure. The flow meter and visual
inspection of the scrubber material could warn against a potential lack of
C02 removal.
I may just get me an O2 sensor for $77. Course, I have no O2 to
sense. I love working with almost any type of sensor. Makes me want to
run design a circuit. :-)
Gary
At 06:32 AM 9/12/2002, you wrote:
>Alec, I to am working the O2 & CO2 sensor issue. The www.amronintl.com site
>has a number of analyzers for O2, CO2 and combined units. This is a great
>site. You have to set up an account with them to get prices. Having set up
>an account and checked out their prices, they are definitely set up for
>commercial traffic. Example, rack mounted O2 &CO2 unit (Sub Mk II - CO2,
>O2, Depth) is over $7,000!
>
>Best I have found so far for Oxygen sensor is to use the Maxtec, formally
>Ceramatec, CAG-250 sensor.
>http://www.cisatlantic.com/trimix/Analyzer/analyzer.htm shows how you can
>build a simple unit out of a CAG-250 sensor ($77) and some simple electrical
>components. Since I am using a PLC and a touchscreen display, all I will
>have to do convert the mV signal from the CAG-250, that is proportional to
>O2 partial pressure, into a 4-20 mA signal and waire to my PLC analog input
>module.
>
>So far I have not found a economical CO2 sensor. If anyone has a lead on a
>economical 4-20mA or mV output sensor for CO2, please post.
>
>Cliff
>
>
>----- Original Message -----
>From: "Alec Smyth" <Asmyth@changepoint.com>
>To: <personal_submersibles@psubs.org>
>Sent: Tuesday, September 10, 2002 2:09 PM
>Subject: RE: [PSUBS-MAILIST] sofnolime
>
>
> > Adam,
> >
> > I'm just building my scrubber. What are you using to monitor the O2 and
>CO2? I'm curious if you've come across any economical analyzers you'd
>recommend. Or are you bilding your own?
> >
> > thanks,
> >
> > Alec