Use the Low Alarm Setpoint field to enter the lowest value that this rate of change value will be permitted to attain, after which a low alarm will be triggered.  Correspondingly, the High Alarm Setpoint is used to set a value at which the high alarm should be triggered. 

If the Positive Rate option is selected on the Settings tab, all rates of change will be positive. In this situation, the high alarm is used to warn of excessively high rates of change (whether the changing value is rising or falling). The low alarm could be used to warn of change rates that are too slow.

If the Positive Rate option is not selected, the high alarm will warn only of excessive change rates for values that are rising.  The low alarm setpoint should be set to a negative value to warn of excessive change rates for values that are falling.

The source for these fields may be either a constant, the result of an expression, or the value of a tag.  Please see the topic: Constant, Expression or Tag for more information on selecting between these three choices.

If noise in the system causes a value to fluctuate above and below the setpoint, the alarm will repeatedly switch between active and inactive status.  By using the deadband, you can dampen out these fluctuations by setting an amount by which the tag’s value must retreat back past the setpoint before the alarm state is considered to no longer be active.

For the low alarm, this means that the value must rise <deadband> units above the setpoint.  For the high alarm, the value must fall by <deadband> units below the setpoint.

The deadband is used only for changing a current alarm’s active status. It does not affect the setpoint.

Noise in the value being monitored may cause transient spikes or drops in the reported rate of change.  To avoid having alarms triggered by system noise, you can set a delay in seconds.  The value must meet or exceed the alarm setpoint for the length of the delay time before an alarm will be activated.

The Alarm Priority drop-down lists enable you to set the priority of the alarm(s) that will be triggered. It is not uncommon to have a different priority for low versus high alarms.  See: Alarm Priorities for more information about the following standard options:

•    0 – Event

•    1 – Critical Alarm

•    2 – High Alarm

•    3 – Warning Alarm

•    4 – Notice Alarm

If you have defined your own alarm priority tags, those will also be available for selection.

The Disable … Alarm field enables you to specify whether either the low alarm or high alarm for this tag is enabled. Disabling of alarms is typically used in situations where you wish to avoid false alarms. For example, in the event that routine maintenance is being performed on the equipment represented by this tag, the alarm can be disabled until the maintenance is complete and communications are re-established.

A value of 0 (or any tag or expression that returns 0) means that the alarm has not been disabled. Any value other than 0 in this field indicates that the alarm has been disabled.

The value can be provided via any of a constant, an expression, or a tag.  Please see the topic: Constant, Expression or Tag for help selecting which to use.

If the configuration variable AlarmPopupsEnable is set to 1, then setting either the Low Alarm Popup Enable or the High Alarm Popup Enable, will result in a pop-up dialog being displayed whenever the respective alarm is triggered.  It is strongly suggested that this feature be used sparingly.

The Sound fields can be used to set the sound that will be played when either the low alarm or the high alarm is triggered. These fields can be set to blank, 0, 1, or to the name of a .WAV sound file to be played.

If a Sound field is set to 0, no sound will be played when this alarm is triggered.

If a Sound field is set to blank or 1, an alarm sound whose properties are configured on the associated alarm priority tag will be played (see Alarm).

If a Sound field contains the name of a .WAV sound file, it will override any alarm sound configured for the associated alarm priority tag. When specifying a sound file, you must enter its name and extension (e.g. MySound.wav). The specified sound file must be a .WAV file, and must be stored in the application directory. If the specified sound file is not found, the alarm will revert to using tones as specified in the associated alarm priority tag.