Bias Determination
Inertial measurement calibration routines isolate sensor zero-g offsets by placing accelerometers in specific orientation sequences relative to gravity. A zero-g calibration protocol measures baseline output voltage or digital count when the sensitive axis experiences zero net acceleration. Multi-position tumble tests orient sensor axes perpendicular to the local gravity vector to quantify zero-g offset values.
Precise offset identification enables accurate bias compensation in navigation algorithms.
Sequential Rotation
Multi-axis index heads rotate accelerometers through defined angular positions relative to the Earth’s gravitational field. Inverting sensor orientation 180 degrees separates acceleration scale factor from true zero-g offset values. Mathematical extraction isolates fixed DC offsets from alignment errors and cross-axis sensitivity terms.
Automated rotation stages execute precise angular steps to gather multi-position calibration datasets.
Temperature Correction
Zero-g offset values vary across operating temperatures due to package thermal stress and silicon piezoresistive shifts. Calibration protocols step ambient temperatures across operational ranges while maintaining zero-g positioning. Curve fitting algorithms compute temperature compensation coefficients for storage in non-volatile sensor memory.
Real-time compensation routines apply stored coefficients to subtract thermal offset drift during field operation.
Factory Verification
Post-calibration test runs verify residual zero-g bias error by sampling sensor outputs across full rotation sequences. Automated analysis confirms calculated bias coefficients bring zero acceleration outputs within target LSB tolerances. Standardized procedures mandate calibration verification across temperature limits before releasing sensors for customer integration.
