摘要
差分吸收光谱法(DOAS)应用于固定污染源烟气排放在线监测时,由于外界测量环境恶劣,控制方式对测量气体浓度具有很大的影响。采用PLC模块设计的方法,将紫外差分CEMS系统控制划分为8个功能子程序,并对其控制流程进行研究;提出优化的顺序控制设计法,将流程转化为PLC程序,方便功能扩展;在准确分析外界强干扰磁场的基础上,硬件上加入屏蔽保护,软件上设计快速加权平均法对模拟量数据进行实时采集,并计算出方差对数据进行取舍,同时CRC检验和指令重传机制也提高了数据的稳定性。对SO2实际测量结果表明:PLC设计法使紫外差分CEMS的抗干扰性能提高了1倍以上。
Because of the poor outer space environment, the controlling pattern has huge influence to the concentrations of monitored gas in application of Differential Optical Absorption Spectroscopy （DOAS） to Continuous Emission Monitoring Systems （CEMS）. It adopts the PLC modal design technique to optimize the design process which translating the sequential control into PLC procedures. Based on analysis of the electromagnetic radiation in the outer 8pace, it designs a shield to protect the system from the outside interference, which uses the rapid weighted average method of analog data, variance choosing, 16 - bit CRC checksum and command retransmission to improve the stability. The results of measuring SO2 proves that the PLC design method improves CEMS anti-jamming capability doubly.
