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针对硅微惯性器件中的微小差分电容检测,提出了一种应用于三明治结构差分电容式微机械加速度计的闭环检测电路.通过等电势屏蔽法,相干解调技术和增加激励信号对称性等技术屏蔽杂散电容,抑制了电路噪声和共模误差,提高了检测电路的微弱信号辨识能力;静电力平衡闭环检测克服了开环输出信号的非线性缺陷,实现了高线性度、高分辨率的电容检测.设计的闭环检测电路具有电路简单、线性度好、抗干扰性强和易于集成的特点.实验结果表明,加速度计量程可达±15g,电容分辨率可达10-16F.
Aiming at the detection of tiny differential capacitance in silicon micro-inertial devices, a closed-loop detection circuit applied to sandwich differential micro-mechanical accelerometer is proposed. By means of equipotential shielding method, coherent demodulation technique and increasing symmetry of excitation signal, Stray capacitance, circuit noise and common-mode errors are suppressed and weak signal identification capability of the detection circuit is improved. The closed-loop electrostatic force balance detection overcomes the nonlinear defect of the open-loop output signal and realizes high linearity and high-resolution capacitance Detection.The designed closed-loop detection circuit has the characteristics of simple circuit, good linearity, strong anti-interference and easy integration.Experimental results show that the accelerometer can measure up to ± 15g and the capacitance resolution can reach 10-16F.