Design And Implementation Of Data Acquisition And Transmission System For Environmental Protection

Environmental data acquisition and transmission system is an important part of the environmental monitoring system,mainly for data acquisition and storage of the contaminated site of various types of inspection instrument,and the data processed according to specified protocol will be transmit to the monitoring center of the environmental protection department through Ethernet or GPRS.Through the analysis of the requirements of the HJ-477 standard and the company's Internal Market Research Report,determine the interface`s various and performance indicators,then decide the overall design of the system.Compared with other similar products,it have the following characteristics: more flexibility in the configuration,the separation of main control unit and data acquisition module design,can according to the needs of the customer to expand the number of acquisition module;built-in safety hardware circuits,can guarantee the transmission safety;increases the function of remote control,in the distal instructions to activate or deactivate the pump or the electromagnetic valve.This system chose AT91SAM9X35 to build the core control module,this chip based on ARM9 core,can run embedded Linux system,and then design based on this platform.Through the analysis and calculation,design the serial port expansion circuit,Ethernet expansion circuit,ADC circuit and other circuit module,then to draw the schematic,PCB design,welding,assembly and testing.After testing,the time-sharing multiplexing serial port extend by three state gate circuit,protect by optocoupler isolation and protection circuit,meet the antistatic requirement and rate requirements.ADC circuit meets the accuracy requirements of the expected 1/1000,the other parameters are in line with expectations.