Design Of PXIe Four-channel Isolated Data Acquisition Module

The memory recorder is a new test instrument based on the digital storage oscillograph,and constantly developing.The device not only has the main functions of data acquisition and waveform display of the oscillograph,but also can store and analyze the collected data for a long time through the storage equipment configured by the instrument.The function of storage recorder is determined by its data acquisition function module.At present,the memory recorder products at home and abroad generally use the custom data bus to transmit the collected data,the equipment has almost no expansion performance.In addition,with the continuous development of the testing field,the application scenario of the memory recorder has gradually changed from the monitoring of single low-frequency signals such as temperature and vibration to the monitoring of high-power equipment starting current,capacitor charge and discharge and other complex high-frequency signals.The requirements for the number of channels,isolation performance,sampling rate,storage depth,transmission bandwidth and other performance indicators of the memory recorder are constantly improved.Therefore,based on the advantages of PXIe(Peripheral Extensions for Instrumentation Express)bus with strong expandability,high transmission rate and large throughput,this thesis develops a four-channel isolated data acquisition function module for memory recorder.The multi-channel synchronous data acquisition and storage of the memory recorder can be realized through this function module,which has very valuable practical value in the field of modern data acquisition technology.The main contents are as follows.(1)In view of the problems of few acquisition channels,easy signal interference,slow transmission rate and poor scalability of the functional module of memory recorder in the past,a four-channel isolated data acquisition module is designed based on PXIe bus.First of all,the functional module of this topic is composed of analog part and digital part.The analog part is a four-channel isolated data acquisition circuit,which is suitable for more complex synchronization signal detection scenes.At the same time,the isolation circuit greatly reduces the signal interference among channels.The digital part uses domestic highperformance Field Programmable Gate Array(FPGA)core processor to improve the processing efficiency of the overall data acquisition module.(2)The data transmission link between the function module and the storage recorder system is designed to realize the control of the computer to the sub-function module and upload the data collected by the module,and design the driver of the function module based on the embedded Linux operating system in the memory recorder.Direct Memory Access(DMA)technology is applied to improve the Processing efficiency of Central Processing Unit(CPU)in the process of data transmission,improve the overall performance of the memory recorder system,and at the same time,for reading and writing large-capacity files,The method of shared memory mapping is adopted to optimize,improve the data transmission and storage rate between functional modules and the system,and realize DMA data transmission of multiple functional modules through interrupt and blocking mechanism.(3)The developed PXIe bus four-channel isolation data acquisition module is tested and the test results were analyzed.Firstly,the input impedance,isolation performance,power supply and input coupling of the data acquisition module are tested respectively.Then,the data link pass-ability and accuracy of the signal of the data acquisition module are tested,and the technical indicators and functions such as precision and filtering are tested.Finally,the test results are analyzed to verify the feasibility and accuracy of the design.The test results show that the four-channel isolated data acquisition module designed in this paper based on PXIe bus can realize multi-channel data acquisition and data storage,and meet the design function and technical index requirements of the subject.