降低传感器调理电路噪声的研究

Research on Reducing Noise of Conditioning Circuits of Sensor

本文通过对高精度表面轮廓传感器调理电路的研究，总结出降低传感器调理电路噪声的分析方法和具体措施。选用同步积分器代替ＲＣ有源带通滤器，并配以同步解调器构成窄频带测量系统，有效地抑制了电路的噪声和干扰。提出电路参数选取原则和前置放大器设计的一般方法。在传感器与放大器之间采用输入变压器作为阻抗匹配，获得前置放大器的最佳源电阻，实现电路的最佳噪声匹配，所研究的调理电路与自制表面轮廓传感器配合，成功地检测出１ｎｍ的微小位移。本文给出的分析方法与措施，对其它测量系统有借鉴意义。

This paper reports the analyzing methods and specific steps for reducing noise of conditioning circuits by studying the conditioning circuits for surface profile measurement with high precision.The circuits with self designed surface profile sensor has succeeded in detecting micro displacement of one nanometer.Basing on noise theory of electronic system,the noise model of preamplifier is analyzed,the conditioning circuits for surface profile sensors are designed.A synchronizing integrator is employed to construct a narrow band detecting system with a synchronous demodulator based on the dynamical tracking filter rather than the general R.C.active bandpass filter.It is effective to restrain circuits noises and disturbances.The noise model of preamplifier is given and analysed.In order to get low output noise of preamplifier,two ways are employed:one is to reduce the temperature noise of source resistor of the sensor as low as possible;another is to make the work frequency to be resonance frequency as near as possible.FETS and amplifiers are combined to form the preamplifier because FETS own small equivalent input noise,low noise coefficient.And amplifiers can occupy large gains.In order to get optium noise matching between the sensor and the preamplifier,the input transformer matching method which is simple and practical is applied.The design of above circuits and principles for selecting parameters are analyzed in detail.This paper includes four figures and one table.The principles discussed in this paper can be also applied in other measurements.