A novel micro-electrostatic field sensor based on parallel-plate resonator

A vertical-driven resonant micromechanical electrostatic field sensor (EFS) has been firstly developed in this paper. The sensor architecture has three major blocks: a parallel-plate driving electrode, a shielding electrode and a sensing electrode. Unlike other devices, there are many holes in the shielding electrode for modulating the electric field. For improving the signal-to-noise ratio (SNR), a differential driving structure is used in the sensor design, and detecting this second-harmonic sensing signal allows the feedthrough signal at the drive frequency to be largely rejected. Based on a digital lock-in amplifier system, we achieve a nonlinearity of 2.8% (end-point-straight-line) at resonant frequency (11.8 kHz) in measurement the range of 0~33kV/m with a driving voltage of 2Vp-p for our prototype device. The device demonstrates lower driving voltage and lower power dissipation than previously MEMS-based EFS. For further improving the performance of the sensor, a closed-loop feedback driving resonant EFS is presented.