Configure PDBC instructions

Use the
Advanced
 tab on the
PDBC Properties
 dialog box to:
  • Set thresholds where outputs (Raise, Lower, and Q) turn on and off,
  • Set thresholds where deviation status bits and their alarms are triggered, and
  • Set thresholds where high rate of change status bits and their alarms are triggered.
  • Set maximum and minimum values for setpoint clamping limits and input PV ranges.
  • Set rate of change time base.
To configure Process Deadband Controller (PDBC) 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. Select the
    Advanced
    tab.
  3. Configure these settings:
    • Drive PV lower at: Threshold limit
      . When the PV is greater than this threshold, the Lower output is energized to drive equipment to reduce the PV.
      For more information on thresholds and deadbands, see Thresholds and deadbands in Process Deadband Controller (PDBC) instructions.
    • PV lower: Deadband
      . Specifies the deadband around the
      Drive PV lower
       threshold. The deadband defines a range below the threshold to prevent unwanted rapid switching of the status.
    • Drive PV higher at: Threshold limit
      . When the PV is less than this threshold, the Raise output is energized to drive equipment to increase the PV.
    • PV higher: Deadband
      . Specifies the deadband around the
      Drive PV higher
       threshold. The deadband defines a range above the limit to prevent unwanted rapid switching of the status.
    • Setpoint clamping limits: Min, Max
      . Sets minimum and maximum limits for operator entries for the Raise and Lower setpoint settings. For example, if the setpoint limits are 20 and 90, an operator cannot enter a setpoint below 20 or above 90.
    • Input PV range: Min, Max
      . Sets the displayed range of the PV that appears as a bar graph on the HMI.
    • PV rate of change time base
      . Sets the rate of change time base. Select per second, per minute, or per hour. To set a custom rate, enter a number of seconds in the
      Units per X seconds
       box. For example, to express the rate of change of the PV in units per day, enter 86400, the number of seconds in a day.
    • Bumpless program/operator/external transition
      . Use this checkbox to define how the instruction setpoint is treated when the owner changes. When selected, in Program the operator and external settings track the program settings; in Operator the program and external settings track the operator settings; in External the program and operator settings track the external settings (transitions are bumpless).
      When not selected, the operator, program and external settings are not modified by the instruction. In this case, when the command source is changed, the effective value of the setting can change depending on the program-set, operator-set, and external-set values.
  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:
      • Deadband, Q is off
      • Deadband, Q is on
      • Above Lower setpoint
      • Below Raise setpoint
      • Same in manual
      • Out of service
    • Device issues
      . When the
      Logix Designer
       application is online with the controller, displays fault status:
      • None
      • Low deviation
      • High deviation
      • High rate of change (decreasing)
      • High rate of change (increasing)
      • Input source bad
      • Configuration error
    • Device mode
      . When the
      Logix Designer
       application is online with the controller, displays the current device mode:
      • Auto
      • Manual
      • Normal
  5. Select
    Apply
    .
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