535-PROF User's Manual
Chapter 7
87
Applications
•
RATE
Alarm occurs when the process variable changes at a rate greater
than what is specified by the alarm setpoint and time base. This alarm
helps to anticipate problems before the process variable can reach
an undesirable level.
For example, if the alarm setpoint is 10 with a time base of 5 sec-
onds, an alarm occurs whenever a change in process variable greater
than 10 occurs in 5 seconds.
ALM.SRC.:1 and ALM.SRC.:2
For HIGH , LOW or HIGH/LOW alarms, specifies the variable (source)
upon which a selected alarm is based. Selection includes:
•
PV
•
PV2
•
SP
•
RAMP SP
•
DEVIATION
•
OUTPUT
ALARM SP:1 and ALARM SP:2
Defines the point at which an alarm occurs. For a RATE (rate of change)
alarm, it specifies the amount of change (per RATE TIME period) that
must occur before the alarm activates. A negative value specifies a nega-
tive rate-of-change. Does not apply to HIGH/LOW alarms.
HIGH SP:1 and HIGH SP:2
For a HIGH/LOW alarm, defines the high setpoint at which an alarm oc-
curs.
LOW SP:1 and LOW SP:2
For a HIGH/LOW alarm, defines the low setpoint at which an alarm oc-
curs.
DEADBAND:1 and DEADBAND:2
Specifies the range through which the process variable must travel be-
fore leaving an alarm condition (see alarm examples at the end of this
section). Prevents frequent alarm oscillation or “chattering” if the process
variable has stabilized around the alarm point.
ALM.1 OUT and ALM.2 OUT
For any enabled alarm, selects the output number to which the selected
alarm will be assigned. It is possible to assign both alarms to the same
output relay, thus creating a “global” alarm .
LATCHING:1 and LATCHING:2
A latching (YES) alarm will remain active after leaving the alarm condi-
tion unless it is acknowledged. A non-latching (NO) alarm will return to
the non-alarm state when leaving the alarm condition without being ac-
knowledged.
