Design And Implementation Of High-Precision Acquisition And Transmission Device Based On FPGA

In the process of the aircraft development,the measurement of temperature parameters has important guiding significance for the evaluation of the working state of the aircraft.Due to the complexity of the internal environment of the aircraft,the electromagnetic interference and noise interference are very serious,so the precision of the temperature acquisition equipment is more stringent.In order to meet the requirement of measuring aircraft internal environment temperature,the multi-channel high-precision acquisition transmission device based on FPGA is designed.The device could constantly monitor the internal environmental temperature and achieve acquisition,amplification and encoding of the analog through the 192 thermocouple output.Finally the device will upload the digital to the baseband control equipment.In this thesis,FPGA is used as the main controller to design the multi-channel high-precision data acquisition and transmitting device.The main research objects are Acquisition converter and Acquisition repeater.The have the same hardware circuit and the similar logic programming.To improve the acquisition precision,the hardware and software are detailed designed,and the key technical problems are analyzed and optimized.First of all,the hardware circuit is optimum designed: According to the principle of thermocouple cold junction compensation,proposing the sensor AD8495 K type thermocouple cold end temperature compensation method and AD590 type S thermocouple cold end compensation method;In order to improve the anti-interference ability of the Anti-interference,designing two order low pass filter circuit to filter the useless signal and retain the useful signal.At the same time,the land noise is also investigated and dealt with.Secondly,in the aspect of software design,using FPGA as the controller,through the internal bus to control the acquisition card work time,improve the collection efficiency;using modular programming design,put forward the counter and dual port RAM cache based on the idea of making the program more flexible,more reliable data processing;the application of CAN bus,ensure the normal communication between data gathering and editing transponder converter,improve the reliability of data transmission;Finally,using over sampling averaging algorithm,effectively reduces signal fluctuations,further improve the accuracy of collection.The paper adopts the internal bus structure in hardware and the ROM table and the CAN bus in software.This method can easily change the collection routes and expansion devices,enables the acquisition of forwarding device has inheritance.Lastly,the test platform is built to test the performance of the acquisition and transmission device,to verify the reliability and accuracy of the acquisition.The test results show that the acquisition accuracy is less than 0.5%,which meets the design requirements.