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orcafood · 09/28/2017, 08:31 AM

Though the resolution is low on the CO2 sensors the CO2 levels in the water should not change too quickly. I'm thinking that fact can be abused in combination with a robust outlier rejection (RLS) system to get a more stable approximation. If we combine hundreds of data points over the course of a few minutes a sizable distribution can be generated.

Another option would be boosting the CO2 signal somehow. Perhaps a dye could be used, reactive to CO2, to enable detection via visible light. I'm thinking a dosimeter with a color based detector could work for a while.

Building a more accurate sensor might be feasible as well, they don't seem very complicated. IR led of the proper nm, maybe a laser diode, small tube with air flow and a very accurate IR detector protected with a band pass filter.

wiki seems to disagree though haha, I don't see why a more powerful IR source couldn't get higher resolution.

"The best of these have sensitivities of 20–50 PPM.[1]"

FTIR lists a detection limit of 50 ppb for CO2 in air. Why would it have such a lower detection limit over NDIR?

-- The interferometer used to sweep the spectrum in the FTIR is why the detection limit is lower

09/28/2017, 08:31 AM	#67
orcafood Registered Member Join Date: Nov 2007 Location: Raleigh Posts: 864	Though the resolution is low on the CO2 sensors the CO2 levels in the water should not change too quickly. I'm thinking that fact can be abused in combination with a robust outlier rejection (RLS) system to get a more stable approximation. If we combine hundreds of data points over the course of a few minutes a sizable distribution can be generated. Another option would be boosting the CO2 signal somehow. Perhaps a dye could be used, reactive to CO2, to enable detection via visible light. I'm thinking a dosimeter with a color based detector could work for a while. Building a more accurate sensor might be feasible as well, they don't seem very complicated. IR led of the proper nm, maybe a laser diode, small tube with air flow and a very accurate IR detector protected with a band pass filter. wiki seems to disagree though haha, I don't see why a more powerful IR source couldn't get higher resolution. "The best of these have sensitivities of 20–50 PPM.[1]" FTIR lists a detection limit of 50 ppb for CO2 in air. Why would it have such a lower detection limit over NDIR? -- The interferometer used to sweep the spectrum in the FTIR is why the detection limit is lower __________________ Acros, Zoas, Lps and Acros Kevin Current Tank Info: 200 gallon sps Last edited by orcafood; 09/28/2017 at 02:09 PM.