Concept
Out of Reference Range Alarms
The out of reference range alarm monitors variable movements comparing to a reference variable. By setting an upper deviation limit and lower deviation limit, you configure the tolerance the monitored variable can vary from the reference variable before the alarm is triggered. The upper alarm limit of the monitored variable is equal to the reference point current value plus the upper deviation limit. The lower alarm limit of the monitored variable is equal to the reference point current value minus the lower deviation limit.
An out of range alarm with upper deviation limit, lower deviation limit, and deadband set to zero must meticulously follow the reference variable to not trigger the alarm.
For example, you have a reference variable that is designed to follow the optimal room temperature in a office. By connecting the reference variable and the variable from a thermistor, placed in the office, to an out of reference range alarm, you can set up the alarm to trigger when the temperature differs more than 5 °C (41°F) from the reference variable.
You can configure out of reference range alarms using shunt variable, time delay, and deadband. For more information, see Alarm Functions .
Alarm Types
Alarms Overview
Alarm Functions
Out of Reference Range Alarm Properties – Basic Tab
Creating an Out of Reference Range Alarm