Watlow Series 96 - Manual (Page 28)

Alarms
5 . 9 ■ F e a t u r e s Wa t l o w S e r i e s 9 6
An alarm takes some action, usually notifying an operator, when the process temperature leaves a defined
range. A user can configure how and when an alarm is triggered and whether it turns off automatically
when the alarm condition is over. The alarm examples below are for Output 2.
Alarm Hysteresis
Modbus Register #720 r/w; values: (1-9999).
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.
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.
The alarm hysteresis value for Output 2 can be
viewed or changed with Hysteresis 2 [hYS2]
(Output 2 Menu).
Figure 5.9a Alarm settings.
Normal Operating Range
Low Side Alarm Range
High Side Alarm Range
Alarm High Set Point
Alarm Low Set Point
Time
Temperature
Alarm Hysteresis
Alarm Hysteresis
Process or 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 and/or
subtracting offset values from the control set point.
coIf the set point changes, the window defined by the
alarm set points automatically change with it.
Alarm 2 Type [AtY2] (Output 2 Menu) allows you to
view or change whether the Output 2 alarm will
function as a process or deviation alarm.
The alarm deviation value of Output 2 can be
viewed or changed with Alarm 2 High [A2hi] and
Alarm 2 Low [A2Lo] (Alarm Menu).
Alarm Latching
Modbus Register #721 r/w; values: No (0), Yes (1).
A latched alarm will remain active after the alarm
condition has passed. It can only be deactivated by
the user. An alarm that is not latched will deactivate
automatically when the alarm condition has passed.
Alarm 2 Latching [LAt2] (Output 2 Menu) allows
you to view or change whether the Output 2 alarm
will latch. A latched alarm condition that has been
corrected can be reset by pressing the ˆ infinity
key.
Figure 5.9bÍ Alarm latching.
Normal Operating Range
Alarm High
Set Point
Time
Temperature
Alarm Low
Set Point
The alarm state continues until the
temperature drops to the Alarm High
Set Point minus the hysteresis. A
latching alarm could be turned off by
the operator at this point. A non-
latching alarm would turn off
automatically.
The alarm state begins when the temperature
reaches the Alarm High Set Point
Process
Temperature
Alarm Hysteresis
Alarm Set Points
The alarm high set point defines the temperature
that will trigger a high side alarm. The alarm high
set point 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. The alarm low set
point must be lower than the alarm high set point
and higher than the low limit of the sensor range.
Process or deviation alarm set points for Output 2
can be viewed or changed with Alarm 2 High [A2hi]
and Alarm 2 Low [A2Lo] (Alarm Menu).