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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.
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?
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?
And could we know how do you set BMM150? And provide all related project code.
Need your feedback to us for further analysis.