PAI PV limits and delays

Use the
PV fail check
 tab on the
PAI Properties
 dialog box to monitor and configure out of range limits and delays for Process Analog Input (PAI) instructions.
To configure PV limits and delays for PAI 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
    PV fail check
     tab.
  3. Configure these settings:
    • Stuck time limit
      . Use the
      Stuck time limit
       to specify the limit, in seconds, after which the instruction indicates that the PV is stuck. If the Input PV does not change, the device providing Input PV might not be operating properly.
    • Out of range
      : Input PV is expected to stay within the value range specified by limits set by the I/O module and the process operation. When the PV value exceeds or falls below the range, there is a risk that the conditions are not normal and the PAI instruction should report the PV Fail state. Limits and deadband are entered in PV raw units.
      • High limit
        . Enter the upper out-of-range threshold for Input PV.
      • Low limit
        . Enter the lower out-of-range threshold for Input PV.
      • Deadband
        . Enter the deadband around PV out of range limits. The deadband defines a buffer zone around the high and low limits to prevent unwanted rapid switching of the status.
    • Delay: On delay
      . Enter the minimum duration (sec) that the Input PV is out-of-range before the instruction reports the PV Fail state. The On-delay time avoids triggering an unnecessary alarm when the PV only briefly overshoots the upper out-of-range limit or undershoots the lower out-of-range limit.
    • Delay: Off delay
      . Enter the minimum number of seconds the PV Input value must remain within the upper and lower range limits before the instruction turns off the PV Fail status. The Off-delay time reduces status chattering.
    • Gate: Gate delay
      . The out-of-range detection is enabled, or gated, by the gate signal, which is an input of the PAI instruction. Use the Gate delay for enabling the out-of-range detection with delay.
    • Fail on PV uncertain
      . Select to trigger the fail state when the PV quality is uncertain.
  4. When online with the controller, monitor the
    Device state
     and
    Device issues
     indicators at the bottom left of the dialog box:
    • Device state
      . Displays the current device state, such as
      PV good
       or
      PV uncertain
      .
    • Device issues
      . Displays fault conditions, such as
      PV bad
       or
      Configuration error
      .
  5. Select
    Apply
    .
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