PCO2 sensor

[jepuskar]

I have read about several companies working on a PCO2 sensor for rebreathers...does anyone know of any in exisitance?

There are several sensors out there right now that do this, but they are mostly in the medical field..so I have seen.

Thanks,

Jason

 

[padiscubapro]

There is only 1 that is currently in use.. This is also a VERY expensive, the basic unit starts at around $18.5k and goes up from there..

from what I hear there has been slightly more than a hundred sold..

 

[jepuskar]

I will look into this....seems like it is very possible from the response I have received from people involved with this kind of sensing equipment.

Thanks,

Jason

 

[idiot fish]

jepuskar


Vaisala do a CO2 sensor thats small enough and will work in 100% humidity.

The link

http://www.vaisala.com/DynaGen_Attachments/Att2441/2441.pdf

 

[jepuskar]

Very nice..

Thank you for this information. I am going to pursue this...

 

[padiscubapro]

idiot fish once bubbled...
jepuskar


Vaisala do a CO2 sensor thats small enough and will work in 100% humidity.

The link

http://www.vaisala.com/DynaGen_Attachments/Att2441/2441.pdf

That sensor would be useless..

4w at 24v ac/dc thats 166ma continuous draw @24v, thats been one of the big issue too much power..

even if you used double lithium cells like cameras use (they are 6v) that would be 4 batteries at about $10 a piece.. most are rated at 1200mah so thats 7.25hrs for $40 just to make a reasonably small pack (probably the size of a pack of cigarettes). sure you can move to rechargeables but now you'll be carrying a pack the sise of a cannister light.


Plus its 15 minutes for full accuracy.. and for 63% of sacle its around 30 seconds... if your co2 is climbing by the time the alarm sounds it may be too late.. co2 events happen FAST.


Plus the key phrase "non-condensing" this immediately precludes a rebreather.

 

[jepuskar]

not only that, but after researching CO2 buildup in rebreathers, I have found that it is not the percentage of CO2 that is bad, it is the Partial Pressure of CO2 (PCO2) that gets us.

I would need a PCO2 sensor.

ugh, the search continues.

 

[padiscubapro]

the type of sensor that as pointed to works by light absorption.. a laser generates a light of a specific wavelength then a tuned sensor measures the received light and the amount of loss is determined.. my GUESS is that it actually is relaying PCO2 since we will assume 1(pressure ata) at the surface so surface po2 = percentage, but at depth this isn't tru.. since under greater pressure the density increases, so does the number of co2 molecules, this should decrease the amount of light penetrating..

 

[madmole]

Yes, this is how the cheap (ie $40) green house detectors work. unfortunately water vapour attenuates the light even faster so its no use in condensing 100% humidity. Been tried lots of times

The way forward is to use the solubility of the Co2 in a base liquid and measure the PH change. You need to arrange a constant cycle though or else your water saturates

The Inspiration has "The most efficient Scrubber ever seen" according to DERA witha near 100% usage before breakthrough. Monitoring the temprature rise through the stack (there is a heat front where the absorbant is active) will let you know where the active front is and as it approaches the top you know its near its end. This is the better approach but it wont spot breakthroughs and some stupid sods will use the scrubber until 5mm of stuff remains at the top cos the meter says so