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FXOS8700CQ Accelerometer calibration

Question asked by Hans-Henrik Fuxelius on Sep 9, 2017
Latest reply on Sep 29, 2017 by Hans-Henrik Fuxelius

After a reflow process with a rebuild simple owen with temperature regulation I got some issues with off set values with accelerometer values X,Y and Z. Ramp down is very coarse - just opening the owen door slightly

 


Raw values of Accelerometer in 4G-range  is X=-470, Y=-642 and Z=-252

 


These values are so off, that it is not possible to adjust the with OFF_X, OFF_Y and OFF_Z

 


The best I get is:

 

    SPI_WriteFXOS(OFF_X, 0b01110111); =>     ~0 mg
    SPI_WriteFXOS(OFF_Y, 0b01111111); => ~-130 mg
   SPI_WriteFXOS(OFF_Z, 0b00111111); =>       ~0 mg

 


Q1) How much does the PCB footprint affect calibration values in production with proper reflow?? ( for simplicity of soldering, pads are much longer now)

 

Q2) For testing purposes, just adding +130 to Y-value, what other affects can it have beside shrinking the dynamic range in Y-led??

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