MEMS Inertial Sensors are miniaturized mechanical structures coupled to capacitive transducers detecting proof-mass displacement from acceleration, rotation, or vibration via coriolis effects and resonant frequencies.

Sensing Principles:

• Capacitive transduction: displacement of proof mass changes gap/area → capacitance change → detected as charge
• Proof mass: suspended spring-damper mechanical resonator
• Coriolis effect in gyroscope: vibratory MEMS; rotation perpendicular to drive axis induces sense-axis displacement
• Accelerometer: proof-mass displacement directly proportional to applied acceleration

Resonator Design:

• Spring constant and mass set natural resonance frequency (typically 10-100 kHz MEMS range)
• High-Q resonator achieved via vacuum-sealed cavity (quality factor 10,000+)
• Damping: controlled via air gap pressure
• Thermal noise floor (Brownian motion): fundamental limit from kT energy

Key Performance Metrics:

• Bias instability: zero-drift over time (stability < 10°/hour for navigation grade)
• Angle random walk (ARW): white noise spectral density of angular rate
• Cross-axis sensitivity: isolation of x/y/z axes
• Bandwidth: ~1 kHz typical for tactical MEMS

Package and Integration:

• MEMS die bonded to ASIC readout electronics in same package
• Tri-axis accelerometer: three orthogonal proof masses
• Integrated gyroscope+accelerometer: 6-axis IMU for inertial navigation
• Sensor grades: automotive (1-10°/hour drift), tactical (0.1-1°/hour), strategic navigation

Applications and Market: Consumer/automotive/aerospace use MEMS IMU for dead-reckoning, gesture recognition, and stabilization—cost-effective alternative to large ring-laser gyros or fiber-optic gyros for non-navigation applications.