Dual-mode temperature compensation for a comb-driven MEMS resonant strain gauge

A novel vibration mode pair is proposed for the dual-mode temperature compensation of MEMS-scale double-ended tuning fork (DETF) resonant strain gauges excited using comb drives. The mode pair does not require a redesign of the resonator, which was originally optimized for maximum strain sensitivity. Instead, the two different vibration modes are chosen to take advantage of both the in-plane and the levitation forces present in standard capacitive comb arrays. This approach is similar to dual-mode temperature compensation techniques used in quartz resonators, but differs in that (1) one bending mode and one torsional mode are used and (2) the compensating mode is lower in frequency than the main strain-sensing mode. This choice of mode pairs is further advantageous because no changes are required to the electrodes to excite the lower mode, and the axial strain sensitivity of the DETF is not compromised. By tracking two mode shapes of a resonator, a single resonator can be used to determine both strain and temperature. The DETF exhibits sensitivities of 36 Hz/μϵμϵ and −−7.1 Hz/°°C for the bending mode and 0.7 Hz/μϵμϵ and −−8.3 Hz/°°C for the torsional mode. The experiments confirm the feasibility of these mode shapes for dual-mode temperature compensation of comb-driven DETF resonators.