Watlow EZ-ZONE PM Integrated Controller - Manual (Page 140)

Watlow EZ-ZONE ® PM Integrated Controller • 137 • Chapter 9 Features
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 be-
fore the alarm can be cleared.
Alarm hysteresis is a zone inside each alarm set
point. This zone is defined by adding the hysteresis val-
ue to the alarm low set point or subtracting the hyster- e-
sis value from the alarm high set point. View or change alarm
hysteresis with Hysteresis [`A;hy] (Setup Page, Alarm Menu).
Alarm Latching
A latched alarm will remain active after the alarm condition has passed. It can only be deactivated by the
user.
An active message, such as an alarm message, will
cause the display to toggle between the normal settings
and the active message in the upper display and [Attn]
in the lower display.
Push the Advance Key ‰ to display [ignr] in the up-
per display and the message source in the lower display.
Use the Up ¿ or Down ¯ keys to scroll through pos-
sible responses, such as Clear [`CLr] or Silence [`SiL].
Then push the Advance ‰ or Infinity ˆ key to ex- e-
cute the action.
See the Keys and Displays chapter and the Home Page
chapter for more details.
An alarm that is not latched (self-clearing) will deacti-
vate automatically when the alarm condition has passed.
Turn alarm latching on or off with Latching [`A;LA]
(Setup Page, Alarm Menu).
Alarm Silencing
If alarm silencing is on the operator can disable the alarm output while the controller is in an alarm state.
The process value or temperature has to enter the normal operating range beyond the hysteresis zone to acti-
vate the alarm output function again.
An active message, such as an alarm message, will cause the display to toggle between the normal set-
tings and the active message in the upper display and [Attn] in the lower display.
1. Push the Advance Key
‰ to display [ignr] in the upper display and the message source in the lower dis-
play.
2. Use the Up ¿ and Down ¯ keys to scroll through possible responses, such as Clear [`CLr] or Silence
[`SiL] . Then push the Advance ‰ or Infinity ˆ key to execute the action.
See the Keys and Displays chapter and the Home Page chapter for more details. Turn alarm silencing on or
off with Silencing [`A;Si] (Setup Page, Alarm Menu).
Alarm Blocking
Alarm blocking allows a system to warm up after it has been started up. With alarm blocking on, an alarm is
not triggered when the process temperature is initially lower than the alarm low set point or higher than the
alarm high set point. The process temperature has to enter the normal operating range beyond the hysteresis
zone to activate the alarm function.
If the EZ-ZONE PM has an output that is functioning as a deviation alarm, the alarm is blocked when the
set point is changed, until the process value re-enters the normal operating range. Turn alarm blocking on or
off with Blocking [`A;bL] (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
Normal Operating Range
Alarm High
Set Point
Time
Temperature
Alarm Low
Set Point
Alarm Response with Hysteresis
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