I understand that if location changes the calibration can be affected but the magnetometer calibration looses even if I am at the same location.
How much time do you mean by "extended period of time"? In our case we see that sometimes the device looses calibration even if it is kept in suspend mode for around 5 - 10 mins.
"extended period of time" is certainly not 5-10min. To notice significant changes to the magnetic field you woul need mutiple weeks or months.
I am working on a few more tests like turning radio off and verifying sensor performance and saving callibration values to permenant memory. Will update you soon with the results.
I would be suprised that the RF transmission itself causes an issue, but rather if strong electrical current variation in traces close to the sensor.
If you have issue with the device at rest, it is always alwasy one of 2 things:
Bad data because of change in offset
Change in strong/close electrical currents on your boards
Moving permanent magnets
Bad data because of distortions
Steel in mounting hardware (screws, brackets, shield plates, etc.)
Nickel/Cobalt in battery chemistry
Both cases can be detected with a datalog.
In case #1: Move away the sensor from varying magnetic field sources, or move the magnetic field sources from the sensor
In case #2: Move the sensor away from distortion sources, or compensate for the distortion using Soft-Iron Calibration. Our API supports it even if the feature is not (yet) documented in our datasheet. Unless you already know how to generate this compensation matrix, it is far easier to relocate the sensor.
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