Used to monitor quick variations in a process variable. A Rate-of-Change Alarm Source uses its values specified in variable's units per second.
Rate of Change tab
The available options on this tab are described on the next table.
Available options for the Rate of Change tab
Option |
Description |
|---|---|
Enable |
Enables a Rate-of-Change Alarm |
Change/second |
Indicates the percentage of the monitored variable that can vary per second. This value is calculated based on each variable's reading interval, using the formula ROC = (Current Value - Previous Value) / (Current Instant - Previous Instant). If this rate of change is greater than the specified rate, it is considered in an alarm status |
Message text |
Allows specifying a text displayed to users when this Alarm is in an active condition |
Severity |
Specifies an Alarm level's severity. Available options are Critical, High, Medium, or Low |
Need Ack |
Enables or disables Alarm acknowledgment |
Delay (ms) |
Specifies a delay time, in milliseconds. When this value is equal to 0 (zero, default), no delay is applied |
Return message |
Allows specifying a text message displayed to users when this Alarm returns to its normal status |
Allow shelving |
Enables or disables shelving this Alarm |
Maximum shelving time |
Maximum time, in minutes, this Alarm can remain shelved. Default value of this option is 60, that is, one hour |
Maximum shelve count |
Maximum number of times this Alarm can be shelved. Default value of this option is 0 (zero), that is, no limit |