A new two-beam differential resonant micro accelerometer

A novel uniaxial micro-machined resonant accelerometer is presented. The device working principle is based on the stiffness variations of a beam which is fully clamped to the substrate on one side and clamped to a seismic mass on the other side. A movement of the seismic mass, induced by an external acceleration, causes either a compressive or a tensile stress on the beam, inducing a variation of its stiffness. This variation results in a change of the resonance frequency of the beam. The accelerometer is arranged in a differential structure, with two beams built in such a way that their changes in the resonance frequency have opposite sign. This solution allows obtaining a doubled sensitivity with the same area and allows reducing the non linear behavior. First experimental results show that the device has an overall differential sensitivity ¿f_res/g ¿ 450 Hz/g in the linear range of operation, with an overall area occupation lower than (500 ¿m)².