静电悬浮加速度计电容检测电路变压器桥路设计

THE DESIGN OF TRANSFORMER BRIDGE ON CAPACITANCE DETECTION CIRCUIT OF ELECTROSTATIC LEVITATION ACCELEROMETER

静电悬浮加速度计用于测量非惯性力,是重力卫星的重要载荷,高精度重力场模型的获取对加速度计的分辨率要求很高。电容检测电路是加速度计的核心电路之一,其作用是通过测量差动电容的变化,反映检测质量块微小位移的变化,电容检测电路的噪声水平直接影响加速度计的分辨率。通过对电容检测电路的噪声分析,设计了变压器桥路,降低电容检测电路噪声。结果表明,变压器桥路输出阻抗越大,电容检测电路输出噪声越小,选取典型参数代入桥路输出阻抗公式进行仿真。当桥路谐振频率与电容检测信号工作频率相等时,输出阻抗达到最大。因此桥路设计所选取的参数,应满足使桥路谐振频率与电容检测信号工作频率相等,电容检测电路噪声能够大幅度降低。

Electrostatic levitation accelerometer（ELA）,as a significant part of payload gravity satellite measurement,is used in measuring non-conservative forces. The high accuracy of the gravity field model has high resolution requirements for the accelerometer. The capacitance detection circuit is one of the cores of accelerometer. It is designed to detect very small change of differential displacement through very weak differential capacitance signal and the noise level directly affects the resolution of the accelerometer. The transformer bridge is designed to reduce the noise of circuit through analyzing the noise of the capacitance detection circuit. The results shows that when bridge resonances,there is the largest output impedance. The typical parameters are selected to carry out the simulation. When the resonance frequency of the bridge equals to the frequency of the capacitance detection signal,the output impedance reaches the largest. Therefore,the parameter should be selected when the resonance frequency of the bridge equals to the frequency of the capacitance detection signal to reduce the circuit noise greatly.