High-performance monolithic triaxial piezoresistive shock accelerometers

To meet the requirements of triaxial measurement of high-shock with a high accuracy, monolithic high-performance triaxial piezoresistive accelerometers are developed for 50,000–100,000 × g measure range. An axial-stressed tiny-beam scheme is developed for the X and Y axial elements that features both high sensitivity and high resonant frequency, while a three-beam twin-mass structure is developed for Z-axis element that also features aforementioned high performance. The three sensing elements are monolithically integrated by micromachining techniques of double-sided deep etching combined with piezoresistive processes. The sensor chip of the triaxial accelerometer is 4.4 mm × 2.3 mm × 1 mm in dimensions. A dropping-bar system is used to characterize the accelerometer. The sensitivity in X-, Y- and Z-axes are measured as 2.17, 2.25 and 2.64 μV/g/5 V, respectively, while the corresponding resonant frequency is 308, 303 and 164 kHz. With the dropping bar shocking system, a time-domain separation method is developed, for the first time, to realize precise test of the cross-axis sensitivity. With the novel measurement technique, satisfactory cross-axis sensitivity (not higher than 2.1%) is experimentally obtained for all the three axial elements, which contributes to the high performance of the monolithic triaxial shock accelerometers.