Baseline Bias
Uncompensated output voltage or digital code produced by an accelerometer under zero external gravitational acceleration defines its zero-g bias baseline. Within inertial measurement units, zero g offset stability measures the constancy of this output baseline over extended operating periods and across fluctuating environmental conditions. Small shifts in baseline output introduce velocity and position integration errors in dead-reckoning navigation systems.
The metric isolates sensor bias variations caused by internal mechanical relaxation and electrical aging.
Thermal Sensitivity
Temperature variations induce mechanical stresses within the sensor die and package assembly, shifting the electrical output baseline. In evaluating zero g offset stability, thermal hysteresis testing measures bias repeatability as the sensor undergoes heating and cooling cycles. Differential thermal expansion between silicon elements and substrates causes physical warping, which alters piezoresistive balances or capacitive gaps.
Internal temperature sensors provide real-time data to dynamic compensation algorithms stored within integrated microprocessor memory.
Package Stress
Printed circuit board mounting torque and potting compound curing forces impart mechanical strain that shifts the zero-g bias point over time. High performance zero g offset stability requires stress-isolated package designs, such as surface-mount ceramic enclosures with specialized die attach adhesives. Long-term drift evaluation involves continuously monitoring stationary sensor output under controlled environmental conditions for several hundred hours.
The resulting stability data define the recalibration interval needed for high-accuracy tilt and vibration monitoring instruments.
Calibration Limit
Qualification protocols specify Allan variance analysis to separate short-term noise from long-term bias drift. Sensor specifications define maximum allowable zero g offset drift over operating temperature ranges and shelf life durations.
