I noticed that according to my scd41 the CO2 level at my desk has been abnormally low.
What do you guys think of that? Malfunctioning sensor?
Do you have ASC enabled? Does the datasheet/manual discuss the conditions for ASC to take effect?
No, I didn’t know about asc. I have to read about this.
I find for ASC to work properly the sensor must first be exposed to clean outside air for about a week to calibrate itself and thereafter should be exposed to ambient air at least once a week.
This is not suitable for our use case as it will always be exposed to much higher levels.
I would need to perform a forced recalibration (FRC) to set the reference value manually.
I can’t find information on how to perform this via the Pi’s terminal and i2c.
I only found how some people have done this via an arduino.
You could also just account for the offset by raising your CO2 range/threshold based on the lowest measurement when exposed to an atmospheric CO2 concentration. Alternatively, you could add a calibration function to the Input Module that would allow you to force a calibration with a single click.
I found that the SCD module in mycodo already has a forced calibration function build in.
I used this to set it to 450 for now. I will watch this to see whether this will remain more or less stable for the next week or so. I think I could then calibrate again against the value of another co2 meter.
I have since “calibrated” two more times. I seems to always go low after some time.