| With the more stringent requirements for the degree of automation in various fields of society,the physical quantity to be detected is also increasing daily.The traditional single physical quantity measuring instrument can not meet the needs of development.The requirements for measuring instruments in the measurement field are also developing towards the trend of miniaturization,integration and strong adaptability.Measuring instruments that can measure multiple physical quantities at the same time are the development trend of data acquisition system in the future.That how to design a new multi physical quantity high-precision acquisition system has become the key of problem research.Aiming at the above problems,this Thesis analyzes and designs the highprecision multi physical quantity measurement system from the perspective of hardware.The main research contents of this Thesis are as follows:1)The analysis of multi physical quantity characteristics and design of conditioning schemes: the collection and conversion schemes for signals between different physical quantities are different.This thesis analyzes and designs the special circuits required for the collection and conversion of physical quantities such as strain,temperature,and acceleration into voltage signals by studying the collection principles of these physical quantities;A physical quantity to voltage conversion table was designed based on technical indicators and sensor sensitivity.The commonality of the collection among the three physical quantities was studied through the conversion table and the requirements for signal conditioning of each physical quantity.Finally,a universal design scheme for the collection channel was proposed and designed.The design indicators of this thesis are as follows:the strain is dual channel,and the accuracy requirement is ±(0.4%f.s.+2με).The temperature is dual channel,supporting 8 types of thermocouples including K,E,J,T,N,R,S,B.The accuracy index for different types of thermocouples is ±0.1%f.s.±1℃ for K,E,J,T,and N types,and ±0.1%f.s.±2℃ for temperatures between-200℃ and 0℃;The accuracy index of S-type and R-type is ±0.1% f.s.±3℃;The accuracy index of Type B is ±0.1%f.s.±4℃.The acceleration is a dual channel with an accuracy index of ±0.4%f.s.2)The concrete design of the analog channel: high precision design targets put forward higher requirements for the design of analog channels.Thesis analyzes and designs gradually according to the functional modules.By studying the circuit principle,improving the circuit scheme and the means of device selection,in order to improve the accuracy of signal transmission in the analog channel,a specific circuit including attenuation network,program-controlled gain,filtering and single ended to differential had designed.All research directions focus on the task of improving the acquisition accuracy of analog channel.3)Noise analysis of analog channel: the distribution of the total noise of the hardware circuit had been calculated and analyzed,and the noise limit of the signal conditioning channel had been determined.Under the guidance of noise modeling theory,this Thesis models and calculates each functional module and then puts forward a simplified calculation model.With the designing the calculation formula of the circuit noise,that obtains the specific calculation parameters according to the device selection,and the theoretical prediction value.Finally,this Thesis verifies those with the help of Tina simulation tool.This analysis proves the correctness of device selection from the perspective of noise and proves that the research model can serve as a tool to improve circuit design accuracy under certain conditions.4)Experimental verification and result analysis: After designing the hardware circuit,the physical circuit board was tested and analyzed.This thesis proves that the analysis and design are effective and the design results can meet the design goals by verifying the functionality,noise,and accuracy indicators of all levels of circuits. |
PDF Full Text Request