PPID clamping, rate of change, and scaling limits

Use the
Limits
 tab on the
PPID Properties
 dialog box to set the clamping, rate of change, and scaling limits for Process Proportional + Integral + Derivative (PPID) instructions.
To configure clamping, rate of change, and scaling limits for PPID instructions
  1. On the instruction in the routine, perform one of these actions:
    • On the Ladder or FBD instruction, select .
    • In the Structured Text editor, right-click the tag name and select
      Configure <tag name>
      .
  2. Under
    Advanced
    , select the
    Limits
     tab.
  3. Configure these settings:
    • Clamping limits
      : Enter or monitor the clamping limit values. Use the
      HMI
      tab to configure the labels for unit values.
      • SP limit
        . Set the upper and lower limits applied to setpoint (SP) clamping in PV engineering units.
      • CV limit
        . Set the upper and lower limits applied to constant variable (CV) clamping in CV engineering units.
      • Ratio limit
        . Set the upper and lower limits applied to Ratio clamping.
    • Rate of change limits
      . Enter or monitor the rate-of-change limit values. Use the
      HMI
      tab to configure the labels for unit values.
      • SP limit
        . Set the limits for SP rate-of-change increasing and decreasing applied in clamping. Both limits are positive values entered in engineering units per second.
      • CV limit
        . Set the limits for CV rate-of-change increasing and decreasing applied in clamping. Both limits are positive values entered in engineering units per second.
    • Skip SP rate-of-change limiting in interlock, maintenance and override
      . Select to bypass the SP rate limiter in interlock, maintenance, and override modes.
    • Skip CV clamping in manual or CV shed
      . Select to bypass CV clamping in manual mode or if CV is shed.
    • Skip CV rate of change limiting in manual or CV shed
      . Select to bypass CV rate of change limiting in manual mode or if CV is shed.
    • Scaling limits
      . Enter or monitor scaling limit values. Use the
      HMI
      tab to configure the labels for unit values.
      • PV limit
        . Enter limits used in scaling PV engineering units to %.
      • CV limit
        . Enter limits used in scaling CV engineering units to %. Min value is 0% and Max value is 100%.
  4. When online with the controller, monitor the
    Device state
    ,
    Device issues
    , and
    Device mode
     indicators at the bottom left of the dialog box:
    • Device state
      . When the
      Logix Designer
       application is online with the controller, displays the current device state, such
      SP ramping
       or
      CV held
      .
    • Device issues
      . When the
      Logix Designer
       application is online with the controller, displays fault conditions, such as
      PV uncertain
      ,
      SP fail
      , or
      Configuration error
      .
    • Device mode
      . When the
      Logix Designer
       application is online with the controller, displays the current device mode:
      • Manual
      • Auto
      • Cascade (no Ratio)
      • Ratio
  5. Select
    Apply
    .
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