描述
为了提高PLC控制系统工作的可靠性,可以专门设置一个定时器,作为监控程序部分,对系统的运行状态进行检测。若程序运行能正常结束,则该定时器就立即被清零;若程序运行发生故障,如出现死循环等,该定时器在设定的时间到就无法清零,此时PLC发出报警信号。在设计应用程序时,使用这种方法来实现对系统各部分运行状态的监控。如果用PLC来控制某一对象时,编制程序时可定义一个定时器来对这一对象的运行状态进行监视:该定时器的设定时间即为这一对象工作所需的最大时间;当启动该对象运行时,同时也启动该定时器。若该对象的运行程序在规定的时间结束工作,发出一个工作完成信号,使该定时器清零,说明这一对象的运行程序正常;否则,属运行不正常,发出报警信号或停机信号。监控程序的梯形图如图7所示。图7中定时器T1为检测元件,X001为控制对象动作信号,X002为动作完成信号,M2为报警或停机信号。假设被控对象的运行程序完成一次循环需要50s,则定时器K值可取510(T1为100ms定时器)。当X001=1时,被控对象运行开始,T1开始计时;如在规定的时间内被控对象的运行程序能正常结束,则X002动作,M1复位,定时器T1被清零,等待下一次循环的开始;若在规定时间没有发出被控对象运行完成的动作信号,则判断为故障,T1的触点闭合,接通M2发出报警信号或停机信号。
欧美品牌停产的,常用的“PLC”备品备件
我司产品应用于以下领域:
1,《发电厂DCS监控系统》
2,《智能平钢化炉系统制造》
3,《PLC可编程输送控制系统》
4,《DCS集散控制系统》
5,《智能型消防供水控制系统》
6,《化工厂药液恒流量计算机控制系统》
7,《电气控制系统》造纸,印染生产线,变电站综合自动化控制系列
本特利,英维思,伍德沃德,福克斯波罗、西屋、瑞恩、施耐德莫迪康、ABB、AB、西门子、摩托罗拉、GE发那科、安川、博世力士乐,ACSO,力士乐等各大品牌的DCS系统配件,机器人系统配件,大型伺服系统备件。
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