High resolution capacitance detection circuit for rotor micro-gyroscope

Conventional methods for rotor position detection of micro-gyroscopes include common exciting electrodes (single frequency) and common sensing electrodes (frequency multiplex), but they have encountered some problems. So we present a high resolution and low noise pick-off circuit for micro-gyroscopes which utilizes the time multiplex method. The detecting circuit adopts a continuous-time current sensing circuit for capacitance measurement, and its noise analysis of the charge amplifier is introduced. The equivalent output noise power spectral density of phase-sensitive demodulation is 120 nV/Hz ^1/2. Tests revealed that the whole circuitry has a relative capacitance resolution of 1 × 10^-8.