I am still quite new to this. So pardon the newbie question(s)…
Upon my initial install and test, both A+B were virtually identical in readings. But now after only a couple days use, they are diverging. And I find this troubling as it was my hope/expectation that having 2 sensors would provide consistency and verification of the readings. If they can diverge so far and so quickly, I wonder if I have a problem here?
Also, I am unable to understand/explain why the readings shown when accessed via my LAN are so different from those shown on the map (see attached from a screenshot of 2 side-by-side browser windows)?
Some people with a similar problem found having three sources to be a workable solution. If one of three disagrees, return the value that came up twice.. If three are different, return ERROR.
Thanks for your questions. Taking a look at your sensor, I don’t see any problem with the readings. It is fairly normal for the two laser counters in a sensor to have slightly different readings, as they will naturally intake slightly different samples of air.
Taking a look at your sensor’s readings on the map graph, I would actually say the readings are very well aligned. It is also important to remember that by default settings, you’re looking at US EPA AQI data, which can make small differences in data seem larger than they actually are. Take the numbers in your screenshot, for example, the 40 vs 45 is only actually a difference of about 1 microgram per cubic meter.
Additionally, to answer your second question, by default settings, you’re looking at 10-minute averaged data on the PurpleAir map. The data in your LAN view is a 2-minute average, refreshed every 10 seconds. If you change the “averaging period” setting on the map to “real-time,” you should see values that are much closer together. Though, they still probably won’t be the exact same, because the LAN view updates more frequently.
