User guide

Watlow EZ-ZONE
®
PM PID Controller • 99 • Chapter 9 Features
Alarms
Alarms are activated when the output level, process value or temperature leaves a defined range. A user can
configure how and when an alarm is triggered, what action it takes and whether it turns off automatically
when the alarm condition is over.
Configure alarm outputs in the Setup Page before setting alarm set points.
Alarms do not have to be assigned to an output. Alarms can be monitored and controlled through the
front panel or by using software.
Process and Deviation Alarms
A process alarm uses one or two absolute set points to define an alarm condition.
A deviation alarm uses one or two set points that are defined relative to the control set point. High and
low alarm set points are calculated by adding or subtracting offset values from the control set point. If the set
point changes, the window defined by the alarm set points automatically moves with it.
Select the alarm type with Type [`A;ty] (Setup Page, Alarm Menu).
Alarm Set Points
The alarm high set point defines the process value or temperature that will trigger a high side alarm. It
must be higher than the alarm low set point and lower than the high limit of the sensor range.
The alarm low set point defines the temperature that will trigger a low side alarm. It must be lower than
the alarm high set point and higher than the low limit of the sensor range.
View or change alarm set points with Low Set Point [`A;Lo] and High Set Point [`A;hi] (Operations Page,
Alarm Menu).
Alarm Hysteresis
An alarm state is triggered when the process value reaches the alarm high or alarm low set point. Alarm
hysteresis defines how far the process must return into the normal operating range before the alarm can be
cleared.
Alarm hysteresis is a zone inside each alarm set point. This zone is defined by adding the hysteresis value
to the alarm low set point or subtracting the hysteresis value from the alarm high set point.
View or change alarm hysteresis with Hysteresis [`A;hy] (Setup Page, Alarm Menu).
Normal Operating Range
Low Side Alarm Range
High Side Alarm Range
Alarm High Set Point
Alarm Low Set Point
Time
Temperature
Alarm Set Points and Hysteresis
Alarm Hysteresis
Alarm Hysteresis