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    Nicla Sense Me BMM150 Magnetometer

    Nicla Sense Me BMM150 Magnetometer

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    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.


    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.



    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.


    Anyone has ideas where this is coming from?

    6 REPLIES 6

    Hi Frostily6765,

    compensated Data (blue line in left graphs "norm") jumps randomly to the positive/negative Overflow.
    Jumps randomly issue can be reproduced in SENSOR_ID_MAG virtual sensor. when 400uT magnetic field added in -z direction. We will do further analysis for it.

    FFT of the signals for a static magnetic field is measured a clear peak at 20 Hz.
    Haven't fond the abnormal peak at 20hz in 3D coil environment. Since the max ODR of BMM150 is around 300hz(200hz is limited in BHI sensor hub), please make sure the read interval is stable and should be below 200hz limitation. And the possible reason can be that the driven power of your Helmholtz coils have some 15hz noise.

    Community Moderator
    Community Moderator

    Hi Frostily6765,

    Background algorithm BSX need gyro to do calibration with magnet sensor, please refer the following code to  enable gyro sensor.