A high-performance MEMS capacitive strain sensing system

This paper describes the design of a functional strain sensing module with large dynamic range (80 dB), DC to 10 kHz response, high resolution, and mini size for industrial applications, such as the rolling-element bearings research. The design of the MEMS capacitive strain sensor employs mechanical amplifications of package design and buckle beams as well as the linear differential comb capacitor. The sensor is interfaced with a low noise charge amplifier, mixer, and filter circuits to provide an analog output that demonstrated a resolution of 0.09 microstrains with a maximum range of ±1000 microstrains. The sensor and the electronic circuits, including a temperature sensor, can be integrated on a chip, and packaged as a small functional unit. Additional electronics were integrated with the interface circuit on the chip that provide A/D conversion, radio frequency power supply, and digital signal telemetry to a near-by control unit. Preliminary test results are compared with the design simulation.