ABB DSTX170 57160001-ADK 输入输出I/O模块端子

ABB DSTX170 57160001-ADK 输入输出I/O模块端子

ABB DSTX170 57160001-ADK每完成一次循环操作所需的时间称为一个扫描周期。不同型号的plc，循环扫描周期在1微秒到几十微秒之间。程序计数器这样的循环操作，这是dcs所没有的。这也是使plc的冗余不如dcs的原因。dcs是在运算放大器的基础上得以发展的。把所有的函数和过程变量之间的关系都做成功能块（有的dcs系统称为膨化块）。

dcs和plc的表现的主要差别是在开关量的逻辑解算和模拟量的运算上，即使后来两者相互有些渗透，但是还是有区别。80年代以后，plc除逻辑运算外，控制回路用的算法功能已经大大加强，但 plc用梯形图编程，模拟量的运算在编程时不太直观，编程比较麻烦。但在解算逻辑方面，表现出快速的优点，在微秒量级，解算1k逻辑程序不到1毫秒。

ABB DSTX170 57160001-ADK它把所有的输入都当成开关量来处理，16位（也有32位的）为一个模拟量。而dcs把所有输入都当成模拟量，1位就是开关量。解算一个逻辑是在几百微秒至几毫秒量级。对于plc解算一个pid运算在几十毫秒，这与dcs的运算时间不相上下。

ABB DSTX170 57160001-ADK The time required to complete each cycle is called a scan cycle. Different types of plc, the cycle scan cycle between 1 microsecond to tens of microseconds. Program counter such a loop operation, which is not dcs. This is also the reason why plc redundancy is not as good as dcs. dcs is developed on the basis of operational amplifiers. The relationship between all functions and process variables are made into functional blocks (some dcs systems are called bulked blocks).

The main difference in the performance of dcs and plc is in the logic solution of the switching quantity and the operation of the analog quantity, even if the two later penetrate each other, but there is still a difference. After the 1980s, plc in addition to logic operations, the algorithm function of the control loop has been greatly strengthened, but plc programming with ladder diagram, analog operation in programming is not intuitive, programming is more troublesome. However, in terms of solving logic, it shows the advantage of fast, in the order of microseconds, solving 1k logic programs is less than 1 millisecond.

ABB DSTX170 57160001-ADK It treats all inputs as switching quantities, 16 bits (but also 32 bits) as an analog quantity. dcs treats all inputs as analog quantities, and 1 bit is the switching quantity. Solving a logic is on the order of hundreds of microseconds to milliseconds. For plc to solve a pid operation in tens of milliseconds, which is comparable to the dcs operation time.