Study On A Monolithic Quartz Vibrating Beam Accelerometer With Self-test

Quartz Vibrating Beam Accelerometer(QVBA)realizes the excitation of the beam vibration by utilizing the quartz piezoelectric effect,without applying extra excitation structure comparing to silicon vibrating beam accelerometer.QVBA allows digital output due to the stress frequency effect of the beam.It has long time reliability,simple structure,high precision,wide range and stable characteristics,especially fits for cash-strapped strategic weapon inertial navigation,oil drilling,seismic signal detection and so on.Self-test is a significant function of sensors and is essential for some strict safety applications.Based on the existing monolithic QVBA,this research presents a novel structure with self-test,employing basic electrostatic excitation theory,composed by mass-flexible structure,beam,isolation frame,insulation frame and electrostatic plates.Structure optimization is done based on the existing defections of the accelerometer,after optimization,the scale factor remains unchanged and the accelerometer can simulate the frequency change caused by an acceleration of ±1g.Firstly,this paper introduced basic working principle of QVBA and the structure optimization according to now-existing accelerometer defections and bonding process,which is examined and verified by theoretical analysis and ANSYS simulation.Secondly,regular selftest excitation ways were introduced and electrostatic excitation theory was explained in details in this paper.Meanwhile,the sizes of electrostatic plates were determined by theoretical analysis and ANSYS simulation.After that,the fabrication process was designed and a novel bonding process was developed to meet the structure.The bonding strength was experimentally confirmed.By means of impedance analyzer,the resonance characteristics were evaluated: the frequency is measured to be around 56 KHz,the scale factor is around 50Hz/g and the quality factor is higher than 8000.Finally,combined with oscillation circuit,the monolithic quartz vibrating beam accelerometer system with self-test was formed.After meticulously examination of the system performances,the test results demonstrate that the scale factor is 50.5Hz/g,the bias stability is 24.38μg.