LWN2660-6 ABB

The DCS regards all inputs as analog quantities,and 1 bit is the switch quantity.Solving a logic is on the order of hundreds of microseconds to several milliseconds.For plc to solve a pid operation in tens of milliseconds,which is comparable to the operation time of dcs.

In terms of grounding resistance,PLC may not be very demanding,but DCS must be below a few ohms(usually below 4 ohms).Analog isolation is also very important.

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。

在接地电阻方面，对PLC也许要求不高，但对DCS一定要在几欧姆以下（通常在4欧姆以下）。模拟量隔离也是非常重要的。