| Ultra-sensitive low-noise capacitance position sensor circuits are one of key techniques to produce high-sensitive electrostatic accelerometers/inertial sensors. In this thesis, a charging/discharging capacitance sensor circuit for inertial sensors is discussed. The principle of the charging/discharging capacitance sensor circuit is analyzed, the noise sources in the circuit are calculated, the effect of the performance of the main components to the circuit is analyzed, an integrity noise model is built. A Breadboard is built, showing that the resolution of the capacitance position sensor achieved 6×10-7pF/Hz1/2 at 0.1Hz.Firstly, the fundamental principle of the capacitance sensor is introduced. The charging/discharging capacitance sensor circuit mainly consists of signal carrier generator model, sensor head model, Trans-impedance amplifier(TIA) model, The theory of each module is analyzed, the feasibility of circuit is proved in theory,the sensitivity of the circuit is given in theory.Secondly, the noise sources in the circuit are calculated. The intrinsic noise sources of the charging/discharging capacitance sensor circuit come from the charging/discharging current and the TIA circuit. Both are calculated in detail. The effect of parasitic capacitance in this circuit is evaluated. The resolution of the circuit is given in theory.Finally, test results of the breadboard are shown. The voltage reference, the intrinsic noise of sampling system, the sensitivity and resolution of the circuit have been tested. The results show that the performance of the voltage reference and the intrinsic noise of sampling system satisfy requirements. The sensitivity is close to the theoretical anticipation. Although the resolution of circuit still has a little gap with the theoretical anticipation, the noise has been verified experimentally to be limited by the instability of the excitation signal. |
