Evaluating Thermal Gradient Response in Tactical Inertial Measurement Units
Evaluating tactical IMU thermal gradient response requires measuring dynamic bias shifts during rapid thermal ramps rather than steady state isothermal soak points.
Silicon Capacitive Accelerometer
Inertial Architecture
Micro-machined inertial sensors measure dynamic acceleration and tilt by sensing movement of a suspended proof mass relative to fixed electrodes. A silicon capacitive accelerometer integrates differential sense capacitors with a micromachined spring-mass structure on a single silicon die. Acceleration shifts the central proof mass, altering capacitor gap distances and generating proportional electrical differential signals.
Measurement range is bounded by mechanical stop limits that prevent structural damage under extreme shock conditions. High aspect ratio etching ensures rigid out-of-plane stiffness while maintaining flexitudinal axis sensitivity.
Electrostatic Dynamics
Closed-loop force-balance circuits apply electrostatic forces to hold the proof mass near its zero displacement position. Active feedback improves linearity and extends dynamic range compared to open-loop capacitive detection. Electrostatic spring softening effects alter structural resonant frequency as bias voltages increase.
Damping gas trapped inside cavity structures controls frequency response and prevents mechanical ringing near resonance.
Cross Axis Sensitivity
Orthogonal axis misalignment introduces transverse acceleration response errors into primary output signals. Micro-machined spring asymmetry allows proof mass deflection along non-sensitive axes during multi-axis vibration exposure. Differential electrode layouts minimize common mode noise while isolating primary axis motion.
Substrate stress from package mounting alters zero-g offset stability across operating temperature spans.
Calibration Traceability
Gravitational tilt testing on precision index heads provides primary static acceleration reference values. Centrifuge testing verifies high-g linearity beyond standard gravitational Earth reference field limits. Dynamic calibration uses laser interferometry to measure shaker table displacement during frequency response testing.
Calibration certificates state scale factor accuracy and cross-axis rejection ratios.