Two years...

... Two years! Wow, the time flies!

I've picked up some new wireless tag sensors that can plug in to a USB wall plug and will use fewer button batteries. I am still working to get all those placed, but I've got one in the uninsulated detached garage and one in the study again. I am probably overdue to explain the gradual changes to the monitoring system, but that is not this post.

I did a day of calibration (August 11th) where I pulled all the sensors and put them in one place so that I could make sure that they all had the same sense of temperature and humidity. They were all fairly close, but I tweaked individual sensor calibrations by up to ~0.3 °C for some sensors.

The Netatmo CO₂ sensors were fairly far out since they recalibrate to 400ppm based on the assumption that CO₂ levels drop to 400ppm at least once a week. Normally that would not be an issue, but lockdown. Yes, one of the lesser appreciated impacts from the lockdown is that my CO₂ sensors were underestimating the CO₂ levels in the house from probabaly since July through the 11th of August by 50 to 100ppm.

Placed outside the living room sensor dropped to 352ppm, whereas the bedroom sensors dropped to about 280ppm. They were all recalibrated to ~ 400ppm. In the week following the CO₂ levels in the living ranged from 630 to 980ppm. The master bedroom ranged from 625 to 1025ppm, and the kids ranged from 625 to 1300ppm (a teenaged boy generates a lot of CO₂)! The week prior the living room was reading ranged from 470 to 920ppm, the master ranged 510 to 880ppm, the kids ranged 600 to 880ppm. All that to say that the sensors were reporting downward biased measurements but that the sensors were out by less than ~ 120ppm for the bedrooms and 50ppm for the living room. Normally this automatic recalibration is not an issue as the HRV reduces to the CO₂ levels to ~ 400ppm by after we are out of the house for 4 to 5 hours even with all the windows closed. Without a lock down we are all out of the house for at least 4-5 hours once a week, and of course once summer is here again we will regularly open the windows again.

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