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Topic: Dissolved CO2 sensor (Read 2299 times) previous topic - next topic

I'm looking to build a sensor for an algae project which reads out the dissolved CO2 content of the algae tanks.  This is not easy because the water is opaque and mucky, it's dissolved, not gaseous CO2, and since the pH is not constant in algae tanks, one cannot use a pH calculation.  I've been thinking that I  could 1) filter and remove a small sample which might allow me to use light measure after injecting chemicals into the filtered sample, 2) somehow liberate the CO2 from the water, then measure the gas, or 3) just find a probe that would work in murky water.  However, I've had no luck.  Anyone have any thoughts here?
Thanks!
Cameron

robtillaart


Did a google found very little information. Only this article that describes a way but it might well be too complex (did not read it)
- http://www.springerlink.com/content/x2t2123x19057384/ -
Rob Tillaart

Nederlandse sectie - http://arduino.cc/forum/index.php/board,77.0.html -
(Please do not PM for private consultancy)

MarkT

I think its a hard problem.  And measuring pH won't work naively anyway as dissolved CO2 is in a slow equilibrium with dissolved bicarbonate (though certain enzymes if present speed this up enormously).

There are sensor systems out there, but no idea how expensive: http://uk.mt.com/gb/en/home/products/ProcessAnalytics/DO_CO2_Sensor/Level_2_CO2_family_NOV03/Carbon-CO2/InPro5000i.html  I suspect they only measure CO2, not bicarbonate, so that might be an issue depending on the application.

Mixing a small sample with Ca(OH)2 solution would cause CaCO3 precipitate which could be sensed by photometer perhaps?  Have to filter out the gunk to get good optical clarity first though.  Don't know how sensitive and repeatable that would be.
[ I won't respond to messages, use the forum please ]

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