Watlow Series 920 Microprocessor-Based Ramping Control - Manual (Page 55)

Alarm Types
There are three Alarm Types for each alarm. ALTYPl and ALTYP2 are the
prompts for Alarm 1 and Alarm 2, respectively. The choices are: Process
alarm (P), or Deviation alarm (D).
For review, a “process” type alarm is one that is set at a fixed degree dis-
tance, either positive or negative, from the mean O°F or O°C. A “deviation”
type alarm is always a fixed degree distance, positive or negative, from Set
Point (SP).
If we change SP, a process type alarm remains where it was originally set,
while a deviation type alarm will shift with SP the same number of degrees as
its value. The examples illustrate a plot of each alarm type.
Here we’ve added a process alarm function to the basic graph.
SP1 ,................. . . . . . . . . . . . . . . . . . . . . . . . .
Fixed Distance
from O°
Actual
0°C
Time
This graph shows a deviation alarm setting, and how it shifts with a change in SP.
Temp
SPl
Actual
Deviation Alarm - Fixed Degree distance from
Time
New SP
Figure 32 -
Alarm Type for
Alarm 1 is “process”
alarm (ALTYP =P)
Figure 33 -
Alarm
Type for
Alarm 1 is a “devia-
tion” alarm
(ALTYP=D).
How To Use The Alarms, Chapter 7 WATLOW Series 920 User's Manual 55