Functions of CPB and DB: the cooling P band CPB and the deadband DB are measured in degrees.
5–10 Alarm
There are at most two independent alarms that can be made available by adjusting the alarm special function
parameters A1SF and A2SF. While the descriptions in this section are based on alarm 1, they can also be applied to
alarm 2.
• Latch Alarm: A1SF=LTCH
When selected, the alarm output and indicator latch as the alarm occurs. The alarm output and indicator will be
energized even if the alarm condition has been cleared, unless the power is shut off.
• Hold Alarm: A1SF=HOLD
When selected in any alarm mode, prevents an alarm on power up. The alarm is enabled when the process value
reaches the set point value.
• Latch and Hold Alarm: A1SF=LT.HO
When selected in any alarm mode, prevents an alarm on power up. The alarm is enabled when the process value
reaches the set point value. Thereafter, the alarm acts as a latch alarm as described above.
• Hysteresis (AHY1) adjustment
Example: no special function used with deviation high alarm, SV=100°C, ASP1=10°C, AHY1=4°C
19
PV (
∞
F or
∞
C)
Cooling
Output
100%
CPB
0%
SV+DB
SV
DB Negative
DB Positive
•• No special function: A1SF=
: Alarm on
A1MD
Deviation
high alarm
ON
SV
SV+ASP1
A1MD
Deviation
low alarm
ON
SV
SV+ASP1
(ASP1 negative)
A1MD
Deviation band
high alarm
ON
ON
SV
SV+ASP1
SV-ASP1
A1MD
Deviation band
low alarm
ON
ON
SV
SV+ASP1
SV-ASP1
A1MD
Full scale
high alarm
ON
ASP1
A1MD
Full scale
low alarm
ON
ASP1
112
112
112
112
112
108
108
108
108
108
100
100
100
100
100
ON
OFF
Process proceeds
Below 108
∞
C
alarm off
Below 108
∞
C
alarm off
Below 108
∞
C
alarm off
Above 112
∞
C
alarm on
Above 108
∞
C
alarm stays on
