Limits tab 1756-OF4, -OF8
Use the
Limits
tab on the Module Properties
dialog box to configure output limits on the 1756-OF4 and 1756-OF8 analog output modules. The Limits tab enables you to program clamping and ramp limitations that can prevent damage to equipment. Use the
Limits
tab to:- Enter clamp limits.
- Enable ramping during Run mode.
- Enter a ramp rate.
- Disable or latch clamp alarms.
- Maintain the high and low limit alarms even after the condition ceases.
- Maintain the rate alarm even after the condition ceases.
Parameters
Channel
Select one of the channel buttons to display its information on the alarm configuration tab.
Limits
Enter Limit values for:
- High Clamp- the highest value an output channel will be allowed to reach in the control process
- Low Clamp- the lowest value an output channel will be allowed to reach in the control process
Ramp in Run Mode
Select this box to enable ramping during Run mode. Ramping occurs between the current output level and any new output value received. The output will only be allowed to change at the configured ramp rate limit every 35 milliseconds.
Ramp Rate
Enter the maximum rate of change an output may make in Engineering Units/second. Also serves as a trigger point for a Ramp Rate Limit alarm when the Ramp in Run mode is selected. You can also use the Ramp Rate Limit for ramping to a user-defined value in
Program or
Fault mode. A non-editable copy of the Ramp Rate is shown on the Output State Tab.
Run mode
The controller mode during which logic is executing, inputs are read, the program is scanned, and the outputs are energized and de-energized. Editing operations are restricted. If the keyswitch is in Remote, the controller is in Remote Run mode.
Program mode
The controller mode during which logic is not executing, outputs are not controlled, and editing operations are available. If the keyswitch is in Remote, the controller is in Remote Program mode.
Fault mode
The controller mode entered when a major fault occurs and is not handled by a fault routine or controller fault handler program. Most operations act as if the controller were in Program mode, but it is impossible to switch back to Run mode without clearing the fault condition.
Disable All Alarms
Select this box to disable alarms for the current channel. If selected, all alarm entries beneath this check box are disabled.
The High Clamp and Low Clamp Alarms (see above) are disabled also, but the actual limits themselves are still effective and thus shown above the disable check box.
Latch Limit Alarms
Select this box to maintain the high and low limit alarms even after the condition ceases. The high and low limit alarms are set if the requested output level is beyond either limit (> High or <Low).
Latch Rate Alarm
Select this box to maintain the rate alarm even after the condition ceases. The ramp rate alarm is set if there is a minimum change of input between samples of a channel.
Unlatch
Select this button to unlatch the adjacent alarm condition. Select Unlatch All to unlatch all alarms for the channel.
Slider Bar
Use this bar to visualize where the process limit trigger values are set for your process. You can also drag the process alarm flags to adjust the trigger points.
TIP:
To change the trigger points by whole numbers only, hold down the shift key while dragging the marker on the slider bar.
OK
Select this button to accept your edits on any tab and close the dialog.
Cancel
Select this button to cancel your edits on any tab and close the dialog.
Apply
Select this button to apply your edits on any tab and continue editing.
If:
- You are online in Program, Remote Program or Remote Run mode and,
- This controller is the owner controller and,
- You have changed the module’s configuration in the software,
when you select the Apply or the OK button, the information is automatically sent to the controller. The controller tries to send the information to the module (if the module’s connection is not inhibited). If you don’t select Apply, your changes are not sent to the controller.
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