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4-184 Series 90-30/20/Micro Programmable Controllers Reference Manual – September 1998 GFK-0467K
4
Sample PID Call
The following example has a Sample Period of 100 millisecond, a Kp gain of 4.00 and a Ki gain of
1.500. The Set Point is stored in %R1 with the Control Variable output in %AQ2 and the Process
Variable returned in %AI3. CV Upper and CV Lower Clamps must be set, in this case to 20000 and
400, and an optional small Dead Band of +5 and –5 has been included. The 40 word RefArray
starts in %R100. Normally User Parameters are set in the RefArray with the PID Zoom key F10,
but %M6 can be set to reinitialize the 14 words starting at %R102 (%Ref+2) from constants stored
in logic.
The block can be switched to Manual mode with %M1 so that the Manual Command, %R113, can
be adjusted. Bits %M4 or %M5 can be used to increase or decrease %R113 and the PID CV and
integrator by 1 every 100 millisecond solution. For faster manual operation, bits %M2 and %M3
can be used to add or subtract the value in %R2 to/from %R113 every PLC sweep. The %T1 output
is on when the PID is OK.