Using The Pid Wizard In Step 7-Micro/Win 32 - Siemens SIMATIC S7-200 System Manual

SIMATIC Instructions
The PID loop instruction (Proportional, Integral, Derivative Loop) is provided to
perform the PID calculation. The top of the logic stack (TOS) must be ON (power
flow) to enable the PID calculation. The instruction has two operands: a TABLE
address which is the starting address of the loop table and a LOOP number which
is a constant from 0 to 7. 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.

Using the PID Wizard in STEP 7-Micro/WIN 32

STEP 7-Micro/WIN 32 offers the PID Wizard to guide you in defining a PID
algorithm for a closed-loop control process. Select the menu command
Tools > Instruction Wizard, and then select PID from the Instruction Wizard
window.
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S7-200 Programmable Controller System Manual
A5E00066097-02