- What is the real world accuracy I can expect from this kind of sensor, with and without calibration?
- is it enough for calibration just to go outside and assume some number between 400 and 500 (assuming outside means not just next to industrial chimney)? If not, what would be better calibration process?
I'm using an NDIR-based USB-CO2-meter (~40 €, allegedly USB only for power, but it actually spits out measurement data over USB) and I think it's pretty accurate. When I put it outside it generally reflects ambient CO2 pretty accurately (440-450 ppm) and I found through blind-testing that "air staleness" correlates very well with CO2 concentration. For me, air feels noticeably stale at around ~700-800 ppm, which seems largely inline with academic results.
You can actually see when the device acquires a reading, because the tube flashes.
Re your other questions; yeah I gather there is some experimentation involved, even with out of the box commercial products.
If others have suggestions on chips or products to buy for the household, I would greatly appreciate it! The MH-Z19 looks like an option for me. Commercial products seem too unreliable for the price.
I think that is CO2e, which should be a different thing to my understanding. (CO2e is used to estimate the greenhouse gas potency of other gases like methane. Whereas I think eCO2 is some kind of estimate of amount of CO2 in the air, but what, exactly, I do not know)
because my google-fu was not good enough to find those....
Regardless, I would be curious on the same questions about real world accuracy on those as well.
I have two of them, one inside and one outside. They both go down to roughly 400 ppm and the indoor one goes very high when it's all cooped up inside. The outdoor one fluctuates since I'm in an urban area. I believe they are accurate to within about 10%.
During the smoke event, they combined with my indoor/outdoor pm2.5 sensors have been extremely useful.
You should be using the newer version, MH-Z19B, not MH-Z19.
The protocol is compatible though.
Also note they come in up-to-3000ppm and up-to-5000ppm variants. Be sure to get the latter.
In case it helps anyone: a very fast way to get it working and get graphs is to connect it to a Raspberry Pi running HomeAssistant. Takes a few clicks and 3 lines of config.
https://www.adafruit.com/product/3566
What I was not able quickly to figure out is:
- What this eCO2 actually is?
- What is the real world accuracy I can expect from this kind of sensor, with and without calibration?
- is it enough for calibration just to go outside and assume some number between 400 and 500 (assuming outside means not just next to industrial chimney)? If not, what would be better calibration process?