PAI PV scaling limits and settings

Use the
Advanced
tab on the
PAI Properties
 dialog box to:
  • Set limits for scaling PV value in raw units to PV value in engineering units.
  • Configure settings for the Process Analog Input (PAI) instruction.
To set PV scaling limits and configure settings 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
    Advanced
     tab.
  3. Monitor these parameters:
    • Scaling Limits
    • Clamping snap-to band
  4. Configure these settings:
    • Scaling limits: Scaled
      ,
      Max
       and
      Min
      . Enter PV maximum and minimum values, in engineering/PV units, used in PV scaling.
    • Scaling limits: Input
      ,
      Max
       and
      Min
      . Enter input (unscaled) maximum and minimum values for scaling in raw units. Set the Min and Max values to the range of the signal connected to the raw PV input. The input is then scaled to the values set by the Min and Max engineering (PV) unit values.
      TIP: The PAI instruction supports reverse scaling. Either the raw (Input) or engineering (Scaled) range can be reversed (maximum less than minimum).
    • Substitute PV: Allow substitute PV value
      . Select to enable an alternative source for the PV in Maintenance mode. When selected, the maintenance commands for selecting substitute PV or the input PV are enabled.
    • Enable PV target and deviation calculations
       (entries, displays, and alarms): Select to enable deviation calculations and inform the HMI to make PV deviation visible.
    • Enable rate of change calculations
       (entry, display, and alarm): Select to enable rate of change calculations and inform the HMI to make PV rate of change visible.
    • Time base for rate
      . Select to set the time base for rate.
    • Units per X seconds
      . Type the number of units per x seconds, where x equals the number of seconds selected for the time base for rate.
    • Clamping snap-to band
      . Type the value for the clamping snap-to band. When the difference between the PV and the clamp limits (in %) is less than this value, the PV snaps to the nearest clamp limit (enter
      0
       to disable this feature).
  5. 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
      .
  6. Select
    Apply
    .
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