Watlow EZ-ZONE
®
PM PID Controller • 83 • Chapter 9 Features
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
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
upper display and the message source in the lower
display.
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.
An alarm that is not latched (self-clearing) will
deactivate automatically when the alarm condition
has passed.
Turn alarm latching on or off with Latching
[`A;LA] (Setup Page, Alarm Menu).
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
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 activate the alarm output function again.
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
upper display and the message source in the lower
display.
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 tempera-
ture 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 func-
tioning 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).
Programming the EZ Key/s
You can program the EZ Key either in the Setup
Menu or with configuration software, such as EZ-
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