Alarm Tag Type Properties: Trigger Tab
The Trigger tab for the alarm tag properties folder consists of the attributes used to identify the conditions that the alarm tag will evaluate to determine whether an alarm should be triggered.
The Triggered By property indicates the name of the related tag that is being monitored by this alarm tag. The Setpoint property indicates a user-defined number or another tag whose value is to be used as the Setpoint value that will be compared to the value of the tag being monitored (as identified in the Triggered By tab). The Function property indicates the operation that is to be performed to compare the monitored tag's value with the Setpoint value.
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The Triggered By field enables you to specify the name of the tag whose value will be monitored and compared to the value of this alarm tag's Setpoint value to determine if this alarm should be triggered.
The Triggered By field can be used to associate this alarm tag with a new or existing numeric tag using the tag browser button to its right. The Triggered By field can be cleared of its current value using the X button to its right.
Right-clicking the name of the I/O tag that has been selected in the Triggered By field opens the tag properties folder for the selected communication driver tag.
The Function drop-down list enables you to select one of 11 operators to use to compare the value of the Triggered By tag with the Setpoint value configured for the Setpoint field to determine if there is an alarm state.
The Setpoint field enables you to specify the value you wish to be compared to the value of the tag being monitored by this alarm tag.
The valid value for the Setpoint field can be provided via any of a constant, an expression, or a tag. Please see Constant, Expression or Tag for help selecting which to use.
The Deadband field enables you to enter a value indicating how much far the trigger tag’s value must return into the safe zone before the alarm is no longer considered active. Deadband values are used in systems where some analog values fluctuate frequently, sometimes providing a false data reading. For example, the level of fluid in a tank aboard a vessel might shift frequently in high seas, a circumstance that may be perceived as the level of the tank changing, when it is actually not.
The Delay field enables you to enter an amount of time (in seconds or in fractions of a second) that the system will wait before triggering an alarm for this tag. This allows you to disregard transient spikes in value as tag must remain in an alarm state for the amount of time specified in the Delay field before an alarm will be indicated.