呼吸感应体积描记系统中弱信号锁相放大模块的设计

Design of Lock-in Amplifier on Weak Signal Measuring Module in Respiratory Inductive Plethysmography System

在呼吸感应体积描记呼吸测量系统中，需要测量nV-μV级的微弱感生电压信号，而且在测量过程中，做为传感器的电感线圈容易受到测量环境，呼吸运动以外的其他运动和电子噪声等影响。为适应系统测量范围并降低噪声的影响，设计了一种基于AD630锁相放大电路微弱生理信号检测模块。该模块的锁相放大器具有大于0.96的良好线性度，能检测出传感器的感生电压信号，并分离出直流分量，有效地降低噪声对系统的影响，提高了系统测量的精度，并有望应用于其他微弱生理信号检测。

In respiratory inductive plethysmogrphy measuring system, weak induced voltage with the magnitude of nV~μV is usually measured. During the processing period,the inductive coils of sensor vest is easily affected by the measuring environment, movements besides the respiratory ones and electronic noise. A kind of weak physiological signal measuring module is developed for adapting the RIP system and reducing the effects from noises. The module is designed based on lock-in amplifier（ LIA） composed of AD630. The linearity of input-output of lock-in amplifier in the module is above 0 . 9696 . The module can detect the induced voltage and separate the direct voltage,reduce the impacts from the noises and improve the precision of the measuring system. The weak induced voltage measuring module may also be applied to other weak physiological signals detecting.