LabVIEW 2017 Datalogging and Supervisory Control Module Help
»View Product Info
Requires: DSC Module
In the Shared Variable Properties dialog box, select Alarming to display this page. Use this page to enable alarming for a shared variable.
This page includes the following components:
- Enable Alarming—Specifies whether LabVIEW sets alarming for the shared variable.
- Alarms—Displays the active alarms for the shared variable. Use this section to set and edit conditions under which an alarm occurs.
- Enable Alarm—Creates an alarm when you place a checkmark in the appropriate cell. Contains the following options:
- HI—Enables the HI alarm.
- HI_HI—Enables the HI_HI alarm.
- LO—Enables the LO alarm.
- LO_LO—Enables the LO_LO alarm.
- Value— Creates a Boolean or U32 Bit Field alarm.
- Bad Status—Enables an alarm for a bad status.
- Rate of Change—Enables a rate of change alarm.
- Type—Displays the type of the alarm.
- Name—Sets the name of the alarm.
- Alarm On—Sets alarm conditions for Boolean and U32 bit field shared variables.
- Use this option to set the Boolean shared variable to be in alarm state when the value is either TRUE or FALSE.
- Use this option to set the U32 bit field shared variable to be in alarm state when Any bit is in alarm state or only when All bits are in alarm state.
- Level/Change—Sets the Level or Change of the alarm.
- Level—Sets the value, in engineering units, that evokes the alarm condition. The level values of the numeric alarms conform to the following rule: HI_HI level>HI level>LO level>LO_LO level. The shared variable remains in the alarm state until the shared variable value goes below the Level value minus the Deadband value.
- Change—Sets the value that the shared variable value must change in the specified Time to go into an alarm state.
- Deadband/Time—Sets the Deadband or Time of the alarm.
- Deadband (%)—Sets the alarm deadband as a percentage of the full scale range. The Share Variable Engine (SVE) does not clear an active alarm until the percentage difference between the new value and the previous value equals or exceeds the deadband. If you set the Deadband/Time too high, the SVE might not clear the alarm.
- Time (ms)—Sets the amount of time, in milliseconds, in which the shared variable value must change at least the value of Change to go into an alarm state.
- Invert—Determines which bits evoke an alarm on high, 1, and which bits evoke an alarm on low, 0. Enter the value 1 if you want that bit to evoke an alarm when low. In bitwise terminology, the SVE performs an XOR with the Invert value to produce the alarm state. LabVIEW applies the Invert value to the scaled value after applying any relevant scaling masks.
- Mask—Determines which bits LabVIEW uses to calculate the alarm for the shared variable. LabVIEW uses bits with a Mask value 1 in the alarm calculation. Bits with a Mask value 0 do not evoke an alarm, regardless of the values of the bits. In bitwise terminology, the SVE performs an AND with the Mask value to produce the alarm state. LabVIEW applies the Mask value to the scaled value after applying any relevant scaling masks.
- Priority—Sets the priority of the alarm. Enter a value between 1 and 1000, where 1000 is the highest priority.
- Ack Type—Specifies how alarms are acknowledged. Contains the following options:
- Auto (default)—Specifies that LabVIEW acknowledges the alarm when the shared variable value returns to a normal state.
- User—Specifies that LabVIEW does not acknowledge an alarm until you acknowledge the alarm regardless of the alarm state. LabVIEW does not generate any new alarm instance before you acknowledge the existing alarm instance.
- Each Occurrence—Specifies that LabVIEW does not acknowledge an alarm until you acknowledge the alarm. LabVIEW generates a new alarm instance whenever the alarm changes from a normal state to an abnormal state.
|Note If you specify Each Occurrence for this property, LabVIEW may generate a large number of alarm instances before you acknowledge them.|
- Area—Sets a descriptive area name for the alarm. Create alarm areas to acknowledge an entire area of alarms as a single batch operation.
- Description—Sets the description of the alarm.
|Note The Citadel database accepts a maximum description length of 511 characters. If you enter more than 511 characters, the Citadel database saves the first 511 characters as the alarm description.|
- Log?—Enables alarm logging for the alarm. You also must place a checkmark in the Log Alarms & Events checkbox on the Logging page of the Shared Variable Properties dialog box and place a checkmark in the Enable Alarms and Events Logging checkbox on the DSC Settings: Database page of the Project Library Properties dialog box to enable alarm logging.
- Generate event on value change—Specifies whether LabVIEW generates an event when the value of this shared variables changes.
- On user input only—Specifies whether to generate an event on user input only.