Alignment Precision
Resonance mismatch between the primary drive frequency and the secondary sense frequency degrades the sensitivity of high-end Coriolis sensors. In a dual-resonance architecture, the mode-matching frequency split quantifies the distance in hertz between these two operational states. Ideally, this gap reaches zero to maximize the mechanical gain of the system, but manufacturing tolerances usually create a baseline separation.
Frequency Control
Electrostatic tuning electrodes allow for the adjustment of stiffness to close the gap after the sensor is packaged. By applying specific voltages, the operator reduces the mode-matching frequency split until the response of the device peaks. This active alignment compensates for etching errors or material non-uniformity across the wafer.
Stability of the gap is verified by tracking the phase shift between the drive and sense signals.
Operational Penalty
Increased noise floors are common when the frequencies drift apart over time. Larger values for the mode-matching frequency split force the system to operate on the flank of the resonance curve rather than the center. This position reduces the effective sensitivity to physical inputs like rotation or acceleration.
Temperature shifts often pull the frequencies in different directions, requiring continuous adjustment from the control loop.
Measurement Limit
Successful calibration identifies the minimum possible mismatch achievable with the available voltage. If the mode-matching frequency split cannot be reduced below a certain floor, the device will fail to meet precision specifications. Environmental shocks can physically warp the frame and reset the split to an uncorrectable value.
Maintenance routines prioritize checking this value during regular diagnostic intervals to ensure sensor health.
