Apollo MSR-1 SCD40 CO2 Sensor Installation 

Hello, thanks for the question. The SCD40 does have an auto calibrate that by default runs weekly. We've disabled this (but can be enabled by user) since if the sensor isn't exposed to fresh air, it will greatly throw the SCD40 out of calibration. While the drift due to not calibrating doesn't seem to be in the data sheet, we've not noticed anything drastic with the auto calibration turned off. It holds calibration pretty well and the user can recalibrate anytime they'd like. I've got my AIR-1 with CO2 running for a couple months without calibration and it tracks with a freshly calibrated SCD40. Did you have the auto calibrate on or off during your test? What are you using as a reference to measure that the sensor has drifted? If you haven't yet, feel free to join our discord, there are a lot of really active users there and frequent good discussions. discord.gg/mMNgQPyF94 One last thing to check is the quality/source of the SCD40. There are a lot of cheaper copies of it out there compared to the actual Sensirion unit, that could also always introduce some odd readings possibly. Let us know if this was helpful or if you have any other questions. Datasheet: sensirion.com/media/documents/48C4B7FB/64C134E7/Sensirion_SCD4x_Datasheet.pdf Thanks, Trevor

Thanks a bunch. I have turned off autocalibration, yes, since the whole system didn't look good at all. But then, if I use standard probing, what was that, every 4th second? It climed steadily and after a week, it's climed 100ppm or more. So I tried to change that to every 30s (low power option) which made it drift the other way until it just read 0ppm. I'm quite sure, now, that what I bought is some cheap shite from China. I guess I should try with a real one next time. Where did you get your module, and what was the price? @@ApolloAutomation

Hmm, interesting it changed with the update interval. Ours by default uses the ESPHome default of 60s between readings. Again like with nearly everything, this is configurable by the user. esphome.io/components/sensor/scd4x.html It'll be a little tough to compare since we use the SMD sensor component so we can solder it right to our PCB vs something that might be used with a development/bread board. It is more difficult to know where the breakout modules you find are getting their actual sensor from. Price is a little tough as well since we are doing large quantity buys. I'm a big fan of Octopart for price shopping. octopart.com/search?q=scd40&currency=USD&specs=0&manufacturer_id=921 If you are looking for a breakout board I've had good luck with Adafruit components www.adafruit.com/product/5187 that breakout is $10 cheaper than our MSR-1 with CO2.