Enviro+ Oxide Level slow climb

I have found that if I run the Enviro+ with the supplied python examples for an extended time (hours), that the oxide reading just slowly climbs. It doesn’t ever seem to drop off. I understand that the device takes time to warm up but watching it go from 7k ohms to 18k ohms in a matter of 2 hours on an almost linear curve seems very fishy especially with the data sheet saying 20k ohms is the max. Could have just gotten a faulty unit? Is there a firmware update?

As an update the readings from the python library have stabilized but it is above the specs on the data sheet for the oxidized sensor on the gas sensor. It lists 20k as the max value which correlates to 10 ppm. I have been graphing for a bit now and it does seem to be reading something but it is always in the 22-24k ohms range. Just wondering again if there is some firmware or a library update that is needed or if I have a bad unit?

It’s reading 40k - ish now? I feel like I’m talking to a void though. Again, is there something up with the firmware? These readings are consistently well above the spec on the data sheet for the sensor.

Ummmmm bump? Any Pimoroni employees even in this forum or am I talking to just other users. Or most likely myself?

Pinging people sometimes helps. @sandyjmacdonald is the enviro+ expert.

Thanks monglet, strangely enough I checked the air quality data in my area and 40k would not be out of wack with what my NO2 levels actually are. The problem is the data sheets don’t match up with the readings. That is where I am wondering if there is a firmware issue or if maybe the advertised MICS6814 data sheet is not the exact one that was used? Just looking around for guidance from Pimoroni et al. I may go look at the firmware myself if I can find it on Github.

Well I’ll continue to spam myself for now. I found that the MICS 6814 board reacts differently based on voltage input. Given that most of the Raspberry Pi operates on 5v, my guess is that the Enviro+ is running at 5V which is at the upper limit of the operating voltage on the MICS. This significantly bumps up the readings on the MICS itself (could be as much as a 25% rise in the voltage readings). Again, anyone from Pimoroni on? Maybe they can confirm. I may get on the board with a volt meter if I can find a way around to hit the pins.