PID Controller has primary gain spec zero [ERROR 172]

PID Controller has primary gain spec zero [ERROR 172]

PID Controller Module 4,14,03 Block 4222 has primary gain spec S12 zero

A controller has its overall gain spec set to zero, which will force the output to be 0.0 unless it is tracking.

  • APID: Advanced PID Controller [FC156]
    • S11 is the overall gain multiplier K and must never be 0.
    • S12, S13 and S14 are the KP, KI and KD constants and must never all be 0 (unless one or more of these specs are adapted, in which case there will be no message).
    • S12 must never be 0 if the algorithm is "classical", not "noninteracting", that is, if S18 is 0, 2, 10 or 12.
  • PID: PID Error Input [FC18] and DEL PID: PID Control (PV and SP) [FC19]
    • S5 is the overall gain multiplier K and must never be 0.
    • S6, S7 and S8 are the KP, KI and KD constants and must never all be 0 (unless one or more of these specs are adapted, in which case there will be no message).

The effect of either of the above sets of conditions is that the output is 0.00.

Note that the output is not 0.0 under the following conditions for FC 156 (APID).

  • S4 is wired (this is the TR tracking input)
  • S5 is wired and has a value 1 (this is the TS track switch input)

The image shows live data when tracking is switched on.

APID Tracking Example.png

This message is likely to show an error in the system configuration. It should be reviewed. The issue raised may be in unused logic or graphics, or have other realities that make it a non-issue.

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