The ability of PLC to control switching quantity is very strong.The number of incoming and outgoing points controlled can range from a dozen or tens of points to hundreds,thousands,or even tens of thousands of points.Because it can be connected to the Internet,the number of points is almost unlimited,no matter how many points can be controlled.
The controlled logic problems can be various:combination,sequential;immediate,delayed;not counting,need counting;fixed sequence,random work;etc.,all can be carried out.
The hardware structure of PLC is variable,the software program is editable,and it is very flexible when used for control.When necessary,multiple sets or groups of programs can be written and called as needed.It is very suitable for the needs of multi-working conditions and multi-state transformation in industrial sites.
There are many examples of switching quantity control with PLC.Almost all industrial industries need to use it in metallurgy,machinery,light industry,chemical industry,textile and so on.At present,the first goal of PLC is that other controllers cannot compare with it,that is,it can be used for the control of switching quantity conveniently and reliably.
PLC控制开关量的能力是很强的。所控制的入出点数,少的十几点、几十点,多的可到几百、几千,甚至几万点。由于它能联网,点数几乎不受限制,不管多少点都能控制。
所控制的逻辑问题可以是多种多样的:组合的、时序的;即时的、延时的;不需计数的,需要计数的;固定顺序的,随机工作的;等等,都可进行。
PLC的硬件结构是可变的,软件程序是可编的,用于控制时,非常灵活。必要时,可编写多套,或多组程序,依需要调用。它很适应于工业现场多工况、多状态变换的需要。
用PLC进行开关量控制实例是很多的,冶金、机械、轻工、化工、纺织等等,几乎所有工业行业都需要用到它。目前,PLC首用的目标,也是别的控制器无法与其比拟的,就是它能方便并可靠地用于开关量的控制。
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Kennedy by Theodore C. Sorensen 1965 Harper & Row
SORENSEN/RAYTHEON NARROW RANGE POWER SUPPLY QSA (REF:62
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