Just a follow on up this:
CO sensor now works properly. We tested it in both low and high concentration areas and value goes up and down accordingly.
The problem we're seeing now is in NO2 values. We have 15 of these probes and we tested 5-6 of them. These are the results we're seeing:
- 3 probes are giving us 0.000000 ug/m3 on every measurement, both after 2 min and after 2 hours, without powering the probe off when going to sleep (ALL_ON is used). We tested them in office, outside and in garage on floor -2 where at the same time CO increased from ~800 ug/m3 to ~2300 ug/m3 (3 times).
- One probe mounted outside is giving us ~650 ug/m3 (definitely too high, juding by this document this falls into VERY HIGH category).
- One probe is giving us ~1250 ug/m3 in identical environment as one before.
Air quality stations in our area show that NO2 concentration during the day is usually between 5 and 30 ug/m3
so all these positive values are waaay too high.
PS. SO2 values also look strange. One device (2nd bullet from before) gives us ~300 ug/m3
and other (3rd bullet from before) gives 30-100 ug/m3
. Air quality station in our area shows daily values in range 2 to 20 ug/m3
After fixing a bug in MCP3421.cpp can you confirm that you've tested that all electrochemical sensors work correctly, not just CO?
Do you have any idea why are we getting so inconsistent readings from sensors placed next to each other?
Any idea why some sensors consistently give zero instead of a positive value, where concentrations should increase?