Temperature-drift characterization of a micromachined resonant accelerometer with a low-noise frequency readout

This paper describes the design and experimental evaluation of a silicon micromachined resonant accelerometer with high scale factor and low temperature drift. The device was fabricated by bulk micromachining and sealed in a hermetic metallic package to ensure the resonator operates with high Q-factor. By optimizing the structure, the scale factor of the resonant accelerometer was increased to 361 Hz/g, which is close to the simulated result of 336 Hz/g taking into account the measurement range of ±14 g. The bias-temperature drift coefficient fell to 4.4 μg/°C. A digital frequency readout was implemented using a continuous time stamping method. The measured relative resolution within the operating frequency range of the resonator was better than 1.8 ppb at 1 Hz data update rate. Thus, we have produced a miniaturized resonator accelerator without the bulky commercial frequency counters used in our previous work. A test chamber at a constant temperature varying by only ±0.01°C was used to characterize the temperature drift of the accelerometer prototypes by isolating the disturbances due to the ambient temperature. After increasing the scale factor and decreasing the temperature sensitivity, the 3-day bias stability was measured to be 2.19 μg and 0.51 μg for room-temperature and constant-temperature operations, respectively. Furthermore, the long-term bias stability was 1.77 μg in 30-day measurements when the temperature variations were controlled to be within ±0.01 °C. The experimental results indicate that this resonant accelerometer exhibits excellent long-term temperature stability, which offers the promise for high-performance shipborne inertial navigation applications.