PPID CV clamping limits and CV values

Use the
CV target
 tab on the
PPID Properties
 dialog box to configure control variable (CV) clamping limits and monitor the derivation of the CV target for Process Proportional + Integral + Derivative (PPID) instructions.
To configure CV clamping limits and monitor CV values
  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 the
    General
    tab, select the
    CV target
    tab.
  3. In the
    Operator CV value
     box, enter or monitor the CV target value from the operator when the instruction is owned by the operator or maintenance. If the setting requires a signature, this will enforce security from the HMI and disable the setting from the Logix Designer dialog.
    TIP: Use the
    HMI
    tab to assign a unit label for the values on this tab.
  4. In the
    CV clamping limits
     boxes, enter the high and low clamping limits for the CV.
  5. Monitor these parameters:
    • Device state
      . When the
      Logix Designer
       application is online with the controller, displays the current device state: Manual, PV deviation in deadband, PV deviation not in deadband, SP ramping, CV ramping, Ratio clamped, SP clamped, CV clamped, Windup low, Windup high, SP held, SP set to SPIntlk, CV held, CV set to CVIntlk, Hand, or Initialized.
    • Device issues
      . When the
      Logix Designer
       application is online with the controller, displays fault conditions: None, PV uncertain, Low PV deviation, High PV deviation, Low-Low PV deviation, High-High PV deviation, PV substituted, Interlock trip, SP fail, PV fail, CV 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
    • CV value: Program
      ,
      External
      , and
      Override
      . These boxes display the CV target value when the instruction is owned by Program, External, or Override.
    • Loop mode: Auto
       and
      Cascade
      . Use the 0 and 1 indicators to check the current loop mode. The loop is in Manual mode when the loop is neither Auto nor Cascade and the CV target comes directly from the Operator/Program/External/Override. The loop is open. Otherwise the loop is closed and the CV target is calculated by the PID algorithm from the SP and PV values.
      NOTE:
      For the
      Loop mode
      ,
      CV sheds
      , and
      CV clamping
       configurations:
      • A zero indicates logic false and a one indicates logic true. For example, when the loop is in Cascade loop mode, the indicator next to Cascade is 1.
      • The OR circle is true if any of its inputs is true, and an AND circle is true if all of its inputs are true.
      • A transfer (T) box selects one signal or the other based on the logic state on the diagonal input. When a T appears in a diamond, it is driven by an input from a person, and a T in a square is driven by an input from logic.
    • CV sheds: CV held
       and
      Shed to interlock CV
      . Use the 0 and 1 indicators to check conditions that influence CV target value replacement. The CV target can be overridden by the CV configured for interlock, or held at the last CV value applied, or remain unchanged. Use the
      Advanced > Loop mode
       tab to set the shed action for a specific application.
    • Interlocks
      . Use the button to check or bypass interlocks that can be potentially bypassed. The button is enabled in Online. The button is disabled when the device is out of service. The action is immediate; you do not need to select
      Apply
      .
    • CV clamping
      . Use the 0 and 1 indicators to check conditions that influence CV target value clamping. The CV target value is clamped if the instruction is configured for clamping and either the loop mode is Manual or CV is shed.
    • Last good CV value
      . Displays the value of Val_CVOut to be used with interlock or bad-value CV action.
    • CV target
      . Displays the value of Val_CVSet, the loop CV after clamping and before ramping. The value is in CV engineering units.
  6. Select
    Apply
    .
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