High-gain mechanically amplified capacitive strain sensor

A novel concept of mechanical amplification using buckled beam suspensions and packaging has been demonstrated in capacitive strain sensor design for improved sensitivity. However, the mechanical gain structure introduces a nonlinear characteristic, which degrades the device´s linearity. A 6% nonlinearity was observed at 1000 micro-strain. Therefore, further research efforts are required for improvements. This paper presents an in-depth study of the buckled beams characteristics on nonlinearity analytically and by FEA. The accuracy of the modeling is verified by the measurements. The analysis results show the tradeoff between mechanical gain and linearity, and can be improved by device geometrical optimization. Furthermore, the accuracy of the modeling results in predictable device characteristics, allowing the development of a 2nd order nonlinear electronic compensation method to achieve an overall system performance. Simulation results show that, by applying this technique, the overall system nonlinearity can be greatly reduced from 6% FS to 0.2% FS