sen0321 clips at 20ppb
Joachim.Kock 2026-03-16 04:22:42 143 Views2 Replies I have had the sen0321 ozone sensor for 5 days. It clips the
output from below at 20pbb, meaning that all readings that
should have been below 20 are published as 20. From a graph
showing quite a lot of fluctuation, it is clear that when it
gets down to 20 it is just constant, with no fluctuation at all.
(The graph really looks like clipped audio up-side down.)
No analogue signal could possibly produce this result, so it
looks like a problem with the analog-to-digital conversion.
(I run the unit using esphome. I looked into the code for this
implementation. It is very simple and does not look like it
could be responsible for the clipping. (The code also looks a
lot like the python script provided by DFRobot.))
I am coming to the conclusion that my unit is defect, but I
would be very happy if anybody could comment on the issue,
or even help find a solution.
Dear Yixuan,
thanks a lot for the reply. I recognise your name as the author of the source code! I am honoured you take the time to reply. I have followed your advice of trying out Arduino, but it has taken me some time to learn – I had never tried Arduino before. But finally I figured it out and got the official sample code running. It has been very instructive for me. The symptoms are still the same, though :-( So I will follow your second advice and write to [email protected].
Thanks again!
Joachim.
Joachim.Kock We're sorry to hear you're having this issue with your SEN0321 ozone sensor.
Please first check if you've followed the precautions in our official wiki:
1. The O3 concentration reading will stabilize after about 3 minutes of preheating; please ignore the data during the preheating period.
2. When powering on the sensor for the first time, please keep it powered continuously for 24 hours.
We also suggest testing with our official Arduino sample code. The measuring range of this sensor is 0 to 10 ppm.
If the problem still exists after the above checks, please send your detailed test process and related information to [email protected], and we will help you troubleshoot further.
Yx 
