The Influence Of Multi-phase Medium To The Capacitance Detection Of Micro-gyroscope With Liquid Levitated Rotor

With the development and improvement of microelectronics and MEMStechnology, MEMS transducers have a qualitative improvement in volume, mass,power, precision and many other aspects of performance. The improvement ofintegration has made inertial sensors widely used in military and civilian,especially the silicon accelerometer and gyroscope has been the focus of theresearchers at home and abroad.This paper presented a detection scheme of weak differential capacitive signalfor liquid levitated rotor micro-gyroscope and analyzed the problem of the two-phase or multi-phase flow existing there and the impact of them to the capacitancedetection. The paper mainly includes two aspects, one is the design of weakdifferential capacitance detection circuit, the other one is to analyze the two-phaseflow problem existing in the levitated rotor micro-gyroscope system.For weak capacitance detection circuit, this paper first analysed severalprinciple of weak signal detection, propose the appropriate differential capacitancedetection scheme which is based on the principle of phase-sensitive demodulation,and completed the Hspice simulation of every part of the circuit:the charge circuitamplifier, AC locked amplifier, phase sensitive demoudulation circuit and filtercircuit.The equivalent input noise of simulation is9.8641nV/Hz1/2at100kHz.These proved the correctness of the circuit and then completed the PCB design ofdetection circuit, the equivalent input noise is125nV/Hz1/2and it can achieve theresolution about5107.For the analysis of two-phase flow problem, this paper built a parallel platecapacitor, and put forward a theoretical model of two-phase flow in parallel platecapacitor, and the simulation and experimental results were consistent with thetheoretical model, found that the capacitance and two-phase flow void fractionshowed a linear relationship; also through the experimental test of four kinds ofliquid medium, analyzed the influence of velocity, temperature, excitationfrequency to single-phase liquid medium, all of these helpd to analyze errors ofdetection and guide the choose of liquid media for the levitated rotor gyroscope.