Evaluating Thermal Hysteresis Limits in MEMS Accelerometer Static Leveling
MEMS thermal hysteresis creates non-repeatable zero-g offset shifts up to 3 mg, driving uncompensable arcsecond tilt errors in static leveling systems.
Gravity Vector Projection
Directional Component
Calculation of the directional components of the local gravitational field as they appear along the sensing axes of a stationary instrument. Gravity vector projection provides the primary reference for calibrating inclinometers and multi-axis accelerometers. It assumes that the only acceleration acting on the mass is the constant pull of the earth.
Reference Determination
Local gravity provides a stable and universal signal of exactly one g toward the center of the planet. When a sensor is tilted, the full magnitude of this force is distributed across the X and Y axes according to the sine and cosine of the tilt angles. Comparing the measured values to the expected projection reveals the sensitivity and the bias of each individual channel.
Calibration Routine
Procedures involve rotating the device through a series of known orientations on a precision tumble stand. Each position generates a different set of values that the calibration algorithm uses to solve for the misalignment and the scale factor. An accurate projection requires knowledge of the local gravitational constant, which varies slightly depending on the latitude and the altitude.
Error Mitigation
Vibration or centripetal force can contaminate the measurement by adding non-gravitational acceleration. Filters remove these high-frequency components to isolate the static vector. The resulting data allows the system to determine the orientation of the device relative to the horizon with high precision.