SCD30 ambient pressure help

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javajoesweet
 
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Joined: Sun May 15, 2022 12:45 pm

SCD30 ambient pressure help

Post by javajoesweet »

When I set the ambient pressure value to ~762 on the SCD30 sensor and altitude to 100 meters, the co2 levels increase from ~600 ppm range to ~1000ppm. Is this normal or correct? Also, what values are changeable between self calibration mode and forced calibration mode? Any help would be appreciated. Thanks!

Tim

Code: Select all

    
    # scd.temperature_offset = 10
    logging.debug("Temperature offset: {}".format(scd.temperature_offset))

    # scd.measurement_interval = 4
    logging.debug("Measurement interval: {}".format(scd.measurement_interval))

    scd.self_calibration_enabled = True
    logging.debug("Self-calibration enabled: {}".format(scd.self_calibration_enabled))

    scd.ambient_pressure = 762.06
    logging.debug("Ambient Pressure: {}".format(scd.ambient_pressure))

    scd.altitude = 100
    logging.debug("Altitude: {}".format(scd.altitude))

    # scd.forced_recalibration_reference = 409
    logging.debug("Forced recalibration reference: {}".format(scd.forced_recalibration_reference))

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mikeysklar
 
Posts: 13824
Joined: Mon Aug 01, 2016 8:10 pm

Re: SCD30 ambient pressure help

Post by mikeysklar »

CO2 concentration would normally read lower at higher altitude.

They would also read higher with more atmospheric pressure.

Setting both is not allowed in the CircuitPython driver so it is ignoring your elevation data.
propertyambient_pressure¶
Specifies the ambient air pressure at the measurement location in mBar. Setting this value adjusts the CO2 measurement calculations to account for the air pressure’s effect on readings. Values must be in mBar, from 700 to 1400 mBar
https://docs.circuitpython.org/projects ... tion-notes

I can't tell from looking at the CircuitPython driver exactly which settings are being effected from the calibration modes. They are just registers being set and the SCD30's internal firmware handles it. There are some more details in the calibration guide:

https://sensirion.com/media/documents/3 ... ration.pdf

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