A Double Differential Torsional Accelerometer With Higher Than 10-kHz Measurement Bandwidth for Vibration Monitoring

This article reports the design, fabrication, application-specific integrated circuit (ASIC), package, and characterization of a
${z}$
-axis accelerometer with double differential torsional configuration. Compared with typical comb structures, diagonally large-depth nonpenetrating quad mass has a simple structure with a large feature size. Compared with traditional unbalanced proof mass structures, the fully differential sensitive configuration theoretically eliminates the influence of common mode errors, such as interference force and temperature variations. Thus, a high-performance structure with high sensitivity and good stability was obtained. Meanwhile, the anchor was arranged internally to make the structure more compact and less stress sensitive. The sensitive structure has a size of
$2.4\times1.8$
mm. An optimization of kinetic properties was done to get large bandwidth and small mechanical thermal noise. The ASIC of the double differential torsional structure was implemented, which adopted single-cycle clock double-edge multiplexing to improve
${C}/{V}$
conversion efficiency and reduce circuit noise. At the same time, the error compensation technology used on the ASIC makes the accelerometer sensitivity error less than 1% and zero-bias error less than ±0.02 V. The resonance frequency is about 16 kHz, the ±5% bandwidth is larger than 10 kHz, the cross-axis sensitivities of the
${x}$
-axis and
${y}$
-axis are less than 1.5% and 1%, respectively, the bias instability is less than 700
$\mu \text{g}$
, the noise spectral density is better than 30
$\mu \text{g}/\surd $
Hz above 10 Hz, and the normalized drift over the full temperature range (−40 °C to 60 °C) is less than 1.78 g under uncompensated conditions.