Hi - first a quick explaination of 'where I am coming from' :-
I recently had a quote for the replacement and re-calibration of the CO2 and CO sensors in my Anton Sprint 2000xt - £350 - and the sensors are only good for 2 years - so another £350 in 2 years time !
What is the Anton ? It is a portable combustion gas analyzer - the type used by gas/oil boiler service engineers.
I'm not one of them. My intention is non commercial. I want CO2, CO, and O2 measurements to support a home based combustion project – think furnace – but not heating water or air – its for testing a modified solid fuel burner. ( for my home central heating one day - maybe ? )
Opening up the Anton to get the details of the sensors and lots of Google searches later - I determined the sensors were supplied by citytech.com .
So - a potential project for my arduino ........ if I can find sensors to suit !
Problem : In other posts the MG ( CO2 ) and MQ ( CO ) type sensors have been addressed - the circuitry looks daunting ! and the CO2 reading wont go high enough ( 10000ppm = 1% ) - I need to aim for O2=21%
Reading posts for Lambda sensors - they look scaryierly differcult and some differcult cicuitry - I dont need sensors that tolerate high temperature / pressure changes - as I cool the sample gas and dry it before measurement. Also - they dont appear to be accurate enough for my application - but hard to discern specific numbers for gases detected.
The MG /MQ sensors look pretty cheap - No prices from Citytech - But there is another company - sensorsdirect.co.uk - there sensors look a different technology than the MG /MQ types ( no heaters ? ) and the reading range is considerably wider
The data for the above is limited - but since they are equilvents for citytech sensors ( not for Anton though ! ) - then the sensordirect links should be read in conjungtion with:-
O2 http://www.citytech.com/PDF-Datasheets/4ox1.pdf ( 25% - 2 pin )
these low impedence devices - have such a low output though !
so I don’t get CO2 directly – but it is inferable by chemistry of combustion equation – which can be entered into arduino sketch
But Look : The “7 series” ( below ) has a bigger output 4 – 20 mA dc, and Power supply 10 – 35Vdc
For the electical boffins here : Question : Is there sufficient information in the CityTech pdfs to deduce the support circuitry ? What questions do I need to ask citytech ? ( assuming they will sell to me - as i am not an oem )
thanks for reading