6/7/2014 2:16 PM | |
Joined: 9/27/2006 Last visit: 9/21/2024 Posts: 12282 Rating: (2684) |
Hello pratik; The S7-200 System manual is the best place to locate information on that family of PLCs. In the attachment, you will see the technical data of the S7-200 CPUs, they show that all of them support up to 8 loops in parallel. The closed-loop instructions are described in the S7-200 system manual, starting on page 145 (Chapter 6, Instruction Set): System Manual S7-200 - Siemens Eight PID instructions can be used in a program. If two or more PID instructions are used with the same loop number (even if they have different table addresses), the PID calculations will interfere with one another and the output will be unpredictable. The loop table stores nine parameters used for controlling and monitoring the loop operation and includes the current and previous value of the process variable, the setpoint, output, gain, sample time, integral time (reset), derivative time (rate), and the integral sum (bias). To perform the PID calculation at the desired sample rate, the PID instruction must be executed either from within a timed interrupt routine or from within the main program at a rate controlled by a timer. The sample time must be supplied as an input to the PID instruction via the loop table. So make sure that each loop has a unique loop number, that each required table starts at distinct and non-overlapping addresses in memory, and that all parameters required are correctly written iin the loop tables. Look also at the PIDwizard available on MicroWin, it can make things easier to setup: STEP 7-Micro/WIN offers the PID Wizard to guide you in defining a PID algorithm for a closed-loop control process. Select the Tools > Instruction Wizard menu command and then select PID from the Instruction Wizard window Hope this helps, Daniel Chartier |
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6/7/2014 2:29 PM | |
Joined: 11/26/2009 Last visit: 9/11/2024 Posts: 221 Rating: (1) |
thank you very much |