Monolithic differential vibrating beam accelerometer within an isolating system between the two resonators

In a monolithic differential vibrating beam accelerometer (i.e. the two beams on the same chip), a specific problem, known as "lock-in", appears when the beam frequencies become close due to the applied acceleration. This phenomenon, due to the mechanical coupling between the two beams, leads to a "blind zone" which degrades the VBA accuracy. In this paper, an original differential VBA structure including an isolating system is presented: the principle of operation is explained and recent experimental results show the effectiveness of this system: the measured blind zone is lower than 500 mug, value compatible with the accuracy objective of this concept (a few 100 mug, measurement range plusmn 100 g)