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Comment by ahaucnx | Hacker News Reader

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.

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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

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).

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/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?

That is good confirmation. I bought a MH-Z19 as a pandemic project so I might be approaching that timeframe.

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