3 ms·

I've used both the SenseAir S8 and Sensirion SCD41 sensors, and the SenseAir is clearly my favorite. The SCD41 seems to require a lot more manual calibration w

by breput 2y ago

I've used both the SenseAir S8 and Sensirion SCD41 sensors, and the SenseAir is clearly my favorite. The SCD41 seems to require a lot more manual calibration while the S8 is very stable - maybe once every 3 months or so, I'll see it reporting ~380 ppm in fresh air (which is actually within spec). The venerable MH-Z19 is probably my second favorite sensor, ahead of the SCD40-series.

ahaucnx 2y ago
The MH-Z19 is similar from the performance of the S8 but we do see more noise in the readings and the MH-Z19 also seem to have less life time. We see some of them dying after around 5 years whereas the S8 has a ten year warranty and so far have been rock solid for us.
- breput 2y ago
  That is good confirmation. I bought a MH-Z19 as a pandemic project so I might be approaching that timeframe.
- imjonse 2y ago
  I see all these three (SD40/41, MH-Z19 and S8) on Aliexpress, but in yesterday's discussion on the sibling post it was said that the SD40 is likely a fake since Switzerland based Sensirion do not distribute there. Do you have a blog about sourcing these sensors and those needed for other air measurements? The cheaper options on AliExpress look attractive for someone willing to try a small hobby project but if there's a risk of getting malfunctioning fakes that option may need to be scratched. Thank you
  - ius 2y ago
    I'm not convinced the mere fact that AliExpress sellers are not Sensirion distributors is sufficient to assume these sensors are counterfeit. Obviously there's precedence - buy a 'stm32' and you'll likely receive a counterfeit chip, but that's because these chips have been cloned by many. The Sensirion SCD40 is fairly niche and has an odd form factor - doesn't seem trivial to produce a convincing clone. AliExpress sellers sell these at €14,99/1 whereas DigiKey is at €16,38/600 (excl. VAT). Price seems 'right' to me. I have been looking for a comparison between sensors sourced from AliExpress and a reputable distributor, but sadly couldn't find any. Anyway, I did get a few of these sensors off AliExpress for my personal projects. They definitely measure CO₂ (not eCO₂) - the only issues I've been having with them is the default calibration being off and a struggle to get the temperature reporting right (the sensor suffers from self-heating).
    - bubulina 2y ago
      I ordered one SCD40 and two SCD41 sensor modules from AliExpress and I received them today. According to https://sensirion.com/media/documents/48C4B7FB/64C134E7/Sensirion_SCD4x_Datasheet.pdf https://sensirion.com/media/documents/48C4B7FB/64C134E7/Sens... (page 24) "All SCD4x sensors include a laser marking on the sidewall of the sensor cap. The laser marking contains the product variant (i.e., SCD40 or SCD41) and the product serial number within a data matrix". The SCD40 sensor that I received has the laser marking on the sidewall of the sensor cap, but none of the two SCD41 sensors has it. The price was ~€14 for SCD40 and ~€16 for SDC41. On Digikey they are currently €16.26 for one SCD40 (in a batch of 600) and €21.10 for one SCD41 (also in a batch of 600). What do you think is the lilelihood the SDC41s I received are fake?

by breput 2y ago

ahaucnx 2y ago

The MH-Z19 is similar from the performance of the S8 but we do see more noise in the readings and the MH-Z19 also seem to have less life time. We see some of them dying after around 5 years whereas the S8 has a ten year warranty and so far have been rock solid for us.

breput 2y ago
That is good confirmation. I bought a MH-Z19 as a pandemic project so I might be approaching that timeframe.
imjonse 2y ago
I see all these three (SD40/41, MH-Z19 and S8) on Aliexpress, but in yesterday's discussion on the sibling post it was said that the SD40 is likely a fake since Switzerland based Sensirion do not distribute there. Do you have a blog about sourcing these sensors and those needed for other air measurements? The cheaper options on AliExpress look attractive for someone willing to try a small hobby project but if there's a risk of getting malfunctioning fakes that option may need to be scratched. Thank you
- ius 2y ago
  I'm not convinced the mere fact that AliExpress sellers are not Sensirion distributors is sufficient to assume these sensors are counterfeit. Obviously there's precedence - buy a 'stm32' and you'll likely receive a counterfeit chip, but that's because these chips have been cloned by many. The Sensirion SCD40 is fairly niche and has an odd form factor - doesn't seem trivial to produce a convincing clone. AliExpress sellers sell these at €14,99/1 whereas DigiKey is at €16,38/600 (excl. VAT). Price seems 'right' to me. I have been looking for a comparison between sensors sourced from AliExpress and a reputable distributor, but sadly couldn't find any. Anyway, I did get a few of these sensors off AliExpress for my personal projects. They definitely measure CO₂ (not eCO₂) - the only issues I've been having with them is the default calibration being off and a struggle to get the temperature reporting right (the sensor suffers from self-heating).
  - bubulina 2y ago
    I ordered one SCD40 and two SCD41 sensor modules from AliExpress and I received them today. According to https://sensirion.com/media/documents/48C4B7FB/64C134E7/Sensirion_SCD4x_Datasheet.pdf https://sensirion.com/media/documents/48C4B7FB/64C134E7/Sens... (page 24) "All SCD4x sensors include a laser marking on the sidewall of the sensor cap. The laser marking contains the product variant (i.e., SCD40 or SCD41) and the product serial number within a data matrix". The SCD40 sensor that I received has the laser marking on the sidewall of the sensor cap, but none of the two SCD41 sensors has it. The price was ~€14 for SCD40 and ~€16 for SDC41. On Digikey they are currently €16.26 for one SCD40 (in a batch of 600) and €21.10 for one SCD41 (also in a batch of 600). What do you think is the lilelihood the SDC41s I received are fake?