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    Nicla Sense Me BMM150 Magnetometer

    Frostily6765
    New Poster

    Nicla Sense Me BMM150 Magnetometer

    Hello, 

    we are trying to use the magnetometer on the Nicla Sense Me Board for absolute measurements.

    We measured the values of the Magnetometer in a Helmholtz Coil. We measured the values with an Teslameter and the Nicla. The RAW_Data  of the Nicla for the x, y and z values are consequently wrong about the factor 16 compared to the Teslameter.  

    x-values are applied values of the static field and y-values are measured with the Nicla. The linear approximation shows the factor of ~16 between measured and applied values.

    magnet_verlauf.png

    Furthermore the compensated Data (blue line in left graphs "norm") jumps randomly to the positive/negativ Overflow  ( -32768 or 32767).

    In the attached example we had a magnetic field of 400 uT in z-direction of the sensor and a sample frequency of 1kHz. In the right samples only the RAW data is shown.

    Magnet_1kHz_sampling_400uT.pngMagnet_1kHz_sampling_400uT_RAW.png

      

    Our suggestion is that some bits are shifted falsely here. Can you help us and fix this bug?

    Futhermore, we did an FFT of the signals for a static magnetic field and measured a clear peak at 20 Hz. Therefore we tried applying AC fields, to see if this frequency in the measurement data fits to the applied field frequencies, and if the 20 Hz frequency remains the same. The answer to both unfortunately is no. 

    The picture shows the RAW-data and the FFT for a field with a frequency of 1Hz and the maximum peak at the FFT is at 13 Hz.

    magnet_frequenz.png

    Anyone has ideas where this is coming from?

    4 REPLIES 4
    BSTRobin
    Community Moderator

    Re: Nicla Sense Me BMM150 Magnetometer

    Hi Frostily6765,

    For your feedback, could we know how do you set BMM150? And provide all related project code.

    BSTRobin
    Community Moderator

    Re: Nicla Sense Me BMM150 Magnetometer

    Hi Frostily6765,

    Could you give feedback to us?

    BSTRobin
    Community Moderator

    Re: Nicla Sense Me BMM150 Magnetometer

    Hi Frostily6765,

    Nicla API provide the x ,y ,z in lsb unit rather than uT in SENSOR_ID_MAG_PASS, SENSOR_ID_MAG_RAW virtual sensor.

    We have tested BMM150 in Nicla environment with static magnetic field produced by 3D coil. Haven't fond the abnormal peak at 20Hz. current information how you set up test environment is not enough for further analysis. Could you provide more information about your test environment to us?

    Mag Field Z-axis - uT.png

    Mag Field Z-axis -FFT(AC).png
    And could we know how do you set BMM150? And provide all related project code.

    Need  your feedback to us for further analysis.

    Frostily6765
    New Poster

    Re: Nicla Sense Me BMM150 Magnetometer

    Hello,

    we put the Arduino code and the Matlab code for vizualisation in the attachement. Did you get the bitoverflow for the compensated data? We set up a pair of Helmholtzcoils and measured in this magnetic field. 

    Best regards

     

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