Watlow Series 988LF - Manual (Page 50)

7.4 WATLOW Series 988LF Users Manual Tuning, Manual Operation, Alarms, and Error Codes, Chapter 7
Using Alarms
Output 2 of the Series 988LF can function as an alarm. This is accom-
plished with the [`Ot2] prompt (Setup Menu). If [``Al] is selected, the
output is energized in the non-alarm condition and de-energizes the output
in the alarm condition. Selecting [`ALn] reverses this action: de-energizing
the output in a non-alarm condition and energizing it in an alarm condition.
If the L2 LED on the front panel is lit, this indicates an alarm condition for
output 2.
Once you’ve configured [`Ot2] as an alarm, select the [`ALt] prompt. At
this prompt, you can select the type of alarm: process or deviation.
A process alarm sets an absolute temperature range or process value range.
When the temperature or process leaves the range an alarm occurs. A
process alarm is not tied to the set point.
Example: If your set point is 100°F and a process alarm high limit is set to
150°F and the low limit is set to 50°F, the high limit trips at 150°F, and the
low alarm at 50°F. If you change the set point, the process alarm limits
remain the same.
A deviation alarm alerts the operator when the process strays too far from
the set point. The operator can enter independent high and low alarm
settings. The reference for the deviation alarm is the set point. Any change
in set point causes a corresponding shift in the deviation alarm. Low
alarms are usually set at a negative deviation while high alarms are a
positive deviation.
Example: If your set point is 100°F, a deviation alarm high limit is set to
+7°F and the low limit is set to -5°F, then the high alarm trips at 107°F, and
the low alarm at 95°F. If you change the set point to 130°F, the alarms
follow the set point and trip at 137°F and 125°F.
Alarms can be latching or non-latching. When the alarm condition is
removed, a non-latching alarm automatically clears the alarm output and
alarm message, if one is present. You must manually clear a latching alarm
before it will disappear.
The alarm output is indicated by the corresponding LED on the front panel:
L2. There may be an alarm message flashing in the lower display. When an
alarm message is displayed, it alternately flashes with the current prompt at
a one-second interval in the lower display.
To clear a latching alarm, first correct the condition then press the Auto/
Man key å once.
Alarm silencing is available with all alarms. This function overrides the
alarm on initial power up. On power up, the alarm message will not appear
and the L2 LED and output will reflect a non-alarm condition. Silencing is
active until the process has entered the safe region located between the low-
and high-alarm settings. Then deviation outside this safe zone triggers an
alarm. If an alarm occurs at this point, the output can be silenced by
pressing the Auto/Man key å once, but the controller still displays the
alarm message.
Alarms
NOTE:
An alarm display will
be masked by an error
condition or when the
control is in the
Calibration or Setup
menus.