Watlow Series 998 - Manual (Page 107)

Alarms
WATLOW Series 998 User’s Manual 7.5 Tuning, Alarms and Error Codes, Chapter 7
A flashing lower display indicates an alarm state. Note: If the [Anun]
parameter in the Global Menu is set to [`OFF] the lower display will not
flash and there will be no indication of an alarm state on the front panel.
Once you’ve configured the outputs as alarms, enter the Output Menu
again and select the [`AL3] and/or [`AL4] prompt respectively. These
prompts select the type of alarm, process or deviation. Each may be inde-
pendently set low and high. Choose between process input 1 [`PrA],
process input 2 [`Prb], deviation input 1 [`dEA] or deviation input 2
[`dEb].
Example: [`PrA] can reference the channel A (input 1) process value
against the [A3LO] and [A3HI] settings, or [`Prb] can reference the input
2 process value against the [A3LO] and [A3HI settings.
A process alarm sets an absolute temperature. When the process exceeds
that absolute temperature limit an alarm occurs. A process alarm is
independent from set point.
Example: If your set point is 100°F and a process alarm is set at 150°F
as the high alarm, and 50°F as the low limit, 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 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 and a deviation alarm is set at +7°F
as the high limit, and -5°F as the low limit, 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 trips 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.
There may be an alarm message flashing in the lower display, but if the
[Anun] prompt is set to [`OFF] (located in the Global Menu), no alarm
message is displayed. When an alarm message is displayed, it alternately
flashes with the current prompt at a 1 second interval in the lower dis-
play.
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 is masked
and the output reflects a non-alarm condition. The silencing is active
until the process has entered the safe region located between the low and
high alarm settings. Any future deviation outside this safe region triggers
an alarm. If an alarm occurs at this point, the output can be silenced by
pressing the Auto/Man key once, but the alarm message is still displayed.
NOTE:
An alarm display
will be masked by
an error condition
or when the con-
trol is in the
Calibration or
Setup menus.