uRadMonitor follwup: Dave's unit are down, mine are great, anyone else got one? - Page 1
Forum section: electronics / general

author: moz
author_rank: Regular Contributor
timestamp: December 11, 2019, 03:10:50 am
content: As a followup to:https://www.eevblog.com/forum/reviews/air-quality-monitoring/plus Dave's mailbag and so on. I bought an A3 after the mailbag because it seemed like ma useful thing, and after running it for a while bought two more because I wanted one inside the house as well as outside, and the kids at work wanted in too. Being able to monitor particulates in Sydney at the moment is very useful. Not reassuring, but useful. See imageOutside my house:https://www.uradmonitor.com/tools/dashboard-04/?open=82000117Inside my living roomhttps://www.uradmonitor.com/tools/dashboard-04/?open=82000090Inside the office in Seven Hills:https://www.uradmonitor.com/tools/dashboard-04/?open=82000116I dropped 117 and the wifi module fell off, but I managed to solder it back on and it is working again. But when I run them all in the same place the readings don't match up, and by quite some margin on the CO2 and PM measurements. Which means they're a bit "best guess". Radu has the forums locked down and my "can I calibrate it?" thread is still pending moderation. But I did put up an "I saturated the PM sensor" post.Has anyone else got an idea of how to tweak the calibration of the sensors?

author: thm_w
author_rank: Super Contributor
timestamp: December 13, 2019, 10:55:06 pm
content: 1,000 is crazy high for pm2.5, so thats reasonable if it reads up to that level. Although it could be a software cap as well.CO2 usually have a hardware cap of 2,500 or 5,000 ppm.What is "quite some margin" for CO2 and PM2.5 specifically?Generally the CO2 sensors are self calibrating, so nothing much to do there.

author: moz
author_rank: Regular Contributor
timestamp: December 15, 2019, 07:26:43 pm
content: Right now I'm seeing ~640ppm CO2 and about 440ppm CO2 from two sensors 10m apart with the connecting doors open and the breeze blowing through. That's typical for the difference between them. One of them has to be wrong...

author: moz
author_rank: Regular Contributor
timestamp: December 16, 2019, 05:20:09 am
content: Found an image I prepared earlier - it might appear on the urad forums eventually, but it shows what looks like scaling and offset error. I can drag all three into the office and do a proper comparison but it's somewhat annoying to change the wifi settings so I'd rather not, especially if there's no way to change the calibration.

author: Someone
author_rank: Super Contributor
timestamp: December 16, 2019, 10:37:51 pm
content: There is a huge temperature or humidity sensitivity in those CO2 readings, far higher than the offset shown. Even though we had access to calibration gasses, for most purposes you can use the atmospheric average over a day or two as a calibration.

author: thm_w
author_rank: Super Contributor
timestamp: December 16, 2019, 11:19:00 pm
content: Quote from: moz on December 16, 2019, 05:20:09 amIf those are in the same room then yeah thats a reasonable difference 40ppm. AFAIK 400ppm is generally the lower limit you'd see being outside, so the lower 360ppm reading is suspect.If you really want to pull out the sensor, you could do a zero point cal on that:https://www.winsen-sensor.com/d/files/infrared-gas-sensor/mh-z19b-co2-ver1_0.pdfhttps://www.uradmonitor.com/topic/co2-sensor/Take it outside, then "zero" it at 400ppm. Its going to be a pain in the ass though, if urad does not have that option accessible in the FW.Auto-cal is enabled by default:QuoteIMO though, its close enough to monitor levels you care about, I wouldn't be too worried until it goes over ~1,000ppm, then there is an issue.Quote from: Someone on December 16, 2019, 10:37:51 pmSensor is only using temperature for calibration according to datasheet.

author: moz
author_rank: Regular Contributor
timestamp: December 18, 2019, 07:07:51 am
content: Yeah, it's looking like a lot of effort for something that doesn't especially bother me. It's enough to know the level is going up in the office or not.thanks for the detailed reply.

author: moz
author_rank: Regular Contributor
timestamp: December 27, 2019, 03:14:05 am
content: Outsidethe office in Seven Hills:https://www.uradmonitor.com/tools/dashboard-04/?open=82000116For those interested I've moved that sensor outside. It's not in an ideal location but I'm having trouble finding a place that's got mainsandwifi, and is acceptable to management. The current location probably isn't (it's blu-tacked to a window pane) but since the office is closed for solstice there's no-one there to argue about itSadly reinforced concrete is pretty opaque to wifi frequencies and our good APs all use domain-based authentication that uRad doesn't support so I'm using a test AP with poor coverage.