Siemens PID Control

Hi,

I have been analyzing a Block diagram of the Continuous Controller: PID_CP. Everything seems pretty clear except for one thing.
Within the Process Variable Branch in the Siemens Step 7 it seems you have a choice weather to use a scaled process variable input (PV_IN) or a periferal input (PV_PER). Whats the significant difference? Also, Im not sure how the controller can tell if the PV_PER (Periferal Input) is within Range.

Jeff,

The scaled process variable input is a real number, and the periferal input is a word, or integer I believe.

when you directly use the process variable peripheral, the speed of execution is increased.. When you use manipulated process variable then you are loosing time in scaling it separately..


the max and min values of peripheral variable is 27648 and 0 respectively. as usual in siemens.