Design And Implementation Of A Large Dynamic Signal Conditioning And Acquisition Module

With the rapid development of aerospace,machinery,acoustics,equipment manufacturing and other fields,the use of dynamic signal analyzers has become more and more extensive.As the main tool in the fields of vibration analysis,noise analysis,the dynamic signal analyzer has the functions of signal acquisition,processing and results display as well as real-time analysis of signals below 102.4kHz in the time or frequency domains.It also has the characteristics of large dynamic range,multi-channel independent work as well as rich analysis modes,and widely used in acoustic testing,rotating machinery testing,fault diagnosis and other scenarios.The purpose of this thesis is to design a four-channel dynamic signal analyzer frontend signal conditioning acquisition module with a maximum analysis bandwidth of 102.4kHz and a dynamic range of more than 120dB.The signal input range（auto-ranging）of each channel is 3.99mVpk～31.7Vpk（-51 dBVrms～+27 dBVrms）,the front-end gain adjustment circuit can finely adjust the input signal to the optimal range of the ADC in 2dB stepsize.Structure of dual ADC in single-range-mode,combined with the back-end data processing,has developed it to meet the requirements of the large dynamic range above 120 dB in the fields of acoustics,vibration,and machinery,which makes it possible to measure signals of 1mVpk or even less.The following two points constitute the main work of this thesis:On the one hand,design and implementation of the front-end signal conditioning module with low noise and low harmonic distortion.In order to make full use of the effective number of bits of the ADC to improve the system dynamic range,it is necessary to analyze the noise sources and harmonics inside the signal conditioning channel,according to which we can reasonably design and control the gain adjustment circuits and the mode selection at all levels,so that the effect of out-band spurs and harmonics on the input signal can be minimized.On the other hand,design and implementation of acquisition module based on the technology of dual ADC full-scale dynamic range expansion.Limited to the signal-tonoise ratio index of a single ADC,this thesis introduces a data integration solution in detail.Combined with the circuit structure on which the hardware of single-channel including dual ADC to extend the dynamic range of each range of a single channel,and the experimental simulation verifies its feasibility.Finally,the logic realization of this scheme is expounded.Then a test platform was built,and the debugging and testing of the signal channel conditioning and acquisition board was completed.The test results of various key performance met the requirements of design specifications,which verified the module feasibility of design scheme of the front-end signal conditioning and acquisition channel in this thesis.