Measurements on micromachined silicon accelerometers with piezoelectric sensor action

In this paper, the results of electrical, mechanical (vibration) and electromechanical (sensitivity) measurements on micromachined accelerometer devices with four piezoelectric read-out capacitors are presented. The average capacitance at 1 kHz is 1.2 nF with a Q-factor of 62. The resonance frequencies (in vacuum) of the first two bending modes and the first torsional mode are 12.35 kHz, 26.38 kHz and 17.95 kHz, respectively. The Q-factor of the first bending mode decreases from about 50 in vacuum (0.1 mbar) to 25 at atmospheric pressure. With a sinusoidal excitation at 1.26 kHz, the average accelerometer sensitivity is around 0.1 mV/g; a slight increase of the sensitivity is found in the range from 1 kHz to 6 kHz. (C) 1999 Elsevier Science S.A. All rights reserved.