Watlow Series 94 - Manual (Page 23)

W a t l o w S e r i e s 9 4 A l a r m s a n d E r r o r s ■ 5 . 1
Using Alarms
The Series 94 has a process alarm feature. When the actual temperature
exceeds that absolute temperature limit an alarm occurs. The process alarm set
points may be independently set high and low. Under the Setup Menu, select the
type of alarm output with the
[`Ot2] Output 2 Parameter. [`PrA] sets a
Process Alarm with alarm message displayed. [``Pr] sets a Process alarm with
no alarm message displayed.
Latching: Process alarms can be latching or non-latching. When the alarm con-
dition is removed a non-latching alarm automatically clears the alarm out-
put. You must manually clear a latching alarm before it will disappear by
pressing the RESET key.
Flashing [``LO] or [``HI] in the lower display indicates an alarm when [`Ot2]
is set to [`PrA]. The lower display alternately shows information from the cur-
rent parameter and the [`LO`] or [`HI`] alarm message at one second inter-
vals. The alarm output is de-energized and the Output 2 indicator light is lit.
To clear an alarm: First correct the alarm condition, then:
• If the alarm is latching…
Clear it manually; press the Reset key once as soon as the process tempera-
ture is inside the alarm limits and satisfies the alarm hysteresis
[`HSA].
• If the alarm is non-latching…
The alarm clears itself automatically as soon as the process temperature is
inside the alarm limits and satisfies the alarm hysteresis
[`HSA].
Press once to
clear a latched
and corrected
alarm.
Alarm Silencing is available with the process alarm and has two uses:
When [`SIL] is selected as “on,” the controller automatically disables the alarm
output on initial power up (in either the latching or non-latching mode). Alarm
silencing disables the alarm output relay and the Output 2 indicator light. Once
the process value crosses into the “safe” region, both a latching or a non-latching
alarm is ready. Any future excursion outside of these alarm set points triggers
an alarm.
When [`SIL] is selected as “on,” pressing the Reset Key will disable the alarm
output relay and the Output 2 indicator light once an alarm has occurred, but
will not eliminate the alarm message if enabled. (If
[`Ot2] is set to [`PrA].)
This silences the alarm until the process returns to the “safe” region. Once with-
in this region, the alarm is ready again. Any future excursion outside of the
alarm set points triggers an alarm.
LIMIT 94
RESET
LIMIT 94
RESET
Alarms and Errors
NOTE:
When the alarm out-
put is de-energized,
the N.O. contact is
open in the alarm
condition.
Figure 5.1 -
Clearing a latching
alarm.
5
Alarms and Errors