Design Of Multi-Channel Resistance Signal Acquisition System Based On Wi-Fi Transmission

With the development of precision testing technology,the accurate measurement of electrical resistance plays a vital role in both research and testing.In complex wind tunnel tests,it is often necessary to install various types of resistive sensors at multiple locations to convert various physical quantities into resistive signals for acquisition and transmission,which requires the acquisition system to meet the requirements of high precision,multi-channel,extensibility,and other performance.In order to meet the requirements of precise measurement and reliable transmission of resistance signals in wind tunnel testing,the thesis improves the design of data transmission links,multichannel resistance measurement circuits,and excitation sources.At the same time,it cooperates with software data processing algorithms to design a wireless transmission,multi-channel,high-precision,scalable,and convenient networking resistance signal acquisition system.According to the application background of the system,this thesis determines the functional requirements and performance indicators.The resistance measurement scheme is investigated and the characteristics and sources of error of commonly used measurement methods are studied.Combining the application context and specifications of thesis,the measurement scheme is improved by using an excitation source with a digital potentiometer to form a voltage feedback proportional measurement method.According to the multi-type resistance signal acquisition scenario,a program-controlled voltage and current precision dual excitation source is designed.The three-wire bridge method is used to control the measurement error of the long wire effect,and a programmable bridge circuit with external 1/4 bridge,half bridge and full bridge is designed.A programmed amplification,two-stage filtering and channel isolation conditioning path is designed in the measured signal processing to effectively improve the signal-to-noise ratio of the system.A Wi-Fi based wireless data communication link is used to enhance the scalability and ease of networking.According to the actual system requirements,the system software is divided into driver layer,instrument layer,application layer.To combine the filtering effect with the dynamic response,an adaptive window mean filtering algorithm is designed in conjunction with the 3σ criterion.To reduce system errors,a least squares based data correction algorithm is designed.To address the issues of multi-channel data conflict and communication efficiency,a FIFO circular queue is designed to manage the data,and CPU and dual DMA parallel control are used for data interaction.To address the channel congestion phenomenon when the upper computer communicates with multiple lower computers,Wi-Fi transparent transmission is used to improve the system transmission reliability and stability.Thesis builds a system test platform based on a resistance signal measurement scheme,and tests the functionality and performance indicators of the system.The system can be connected to a local area network through a Wi-Fi router to realize network transmission and channel expansion.The system can measure the resistance change in the range of ±100Ω,and the measurement accuracy is better than 0.07%FS,meeting the system acquisition accuracy index requirements.The system can achieve programmable output of current excitation source from 0.5m A to 10 m A,and programmable output of voltage excitation source from 2.5V to 10 V,and the output accuracy of excitation source meets the requirements of corresponding module index.Comprehensive performance indicators and functional test results of the system in thesis,the system designed in thesis can meet the requirements of convenient networking,scalability,wireless transmission,and high precision resistance measurement.