HEIE431105P1 ABB

In the first generation of PLCs,PLCs were mainly used to replace hard-wired relays and pneumatic timers.In fact,PLCs were called programmable controllers,or PCs for short.But soon,in the early 1980s,the name PC was taken over by the personal computer,so the word PLC was often used.The name PAC appeared about 15 years ago,perhaps to distinguish the most powerful PLC from its lesser brethren.

PLC-based PACs might be a better name than PACs because these controllers incorporate advances made in PLC and other technologies over the past few decades.Manufacturers have adopted proven,more powerful PLC hardware designs and will use the latest,lower-cost technologies from PC and mobile devices.They incorporate these technological advancements to meet changing user needs,providing PLC-based PAC systems.

在第一代PLC时期，PLC主要用于替代硬接线继电器和气动计时器，实际上那时PLC被称为可编程控制器，简称PC。但是很快，在1980年代初期，PC这个名称被个人计算机霸占了，于是就经常使用PLC这个词了。PAC这个名称则出现于大概15年前，它的出现也许是为了将功能最强的PLC从其它稍逊一筹的弟兄们中区分开来。

相较于PAC来讲，基于PLC的PAC也许是更好的名称，因为这些控制器融入了过去几十年中PLC和其它技术所取得的进步。生产制造商已经采用了经验证、更强大的PLC硬件设计，并将从PC和移动设备领域的最新、低成本技术应用其中。它们融合了这些技术进步，以满足不断变化的用户需求，提供了基于PLC的PAC系统。