Omron E5AZ, Руководство пользователя

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81
Loop Break Alarm
Section 4-11
4-11 Loop Break Alarm
4-11-1 Loop Break Alarm (LBA)
• With a loop break alarm, there is assumed to be an error in the control
loop if the control deviation (SP
−
PV) is greater than the threshold set in
the “LBA level” parameter and if the control deviation is not reduced by at
least the value set in the “LBA detection band” parameter within the LBA
detection time.
• Loop break alarms are detected at the following times.
If the control deviation is reduced in the area between 1 and 2 (i.e., the set
point is approached) and the amount the control deviation is reduced is at
least equal to the LBA band, the loop break alarm will remain OFF.
The process value is within the LBA level between 3 and 4, and thus loop
break alarms will not be detected. (The loop break alarm will remain OFF.)
If the process value is outside the LBA level between 4 and 5 and the control
deviation is not reduced by at least the LBA band within the LBA detection
time, the loop break alarm will turn ON.
If the control deviation is reduced in the area between 5 and 6 (i.e., the set
point is approached) and the amount the control deviation is reduced is at
least equal to the LBA band, the loop break alarm will turn OFF.
If the control deviation is reduced in the area between 6 and 7 (i.e., the set
point is approached) and the amount the control deviation is reduced is less
than the LBA band, the loop break alarm will turn ON.
• If the LBA detection time, LBA level, LBA detection band, and PID set-
tings are not appropriate, alarms may be detected inappropriately or
alarms may not be output when necessary.
• Loop break alarms may be detected if unexpectedly large disturbances
occur continuously and a large deviation does not decrease.
• If a loop break occurs when the set point is near the ambient temperature,
the temperature deviation in a steady state may be less than the LBA
level, preventing detection of the loop break.
• If the set point is so high or low that it cannot be reached even with a sat-
urated manipulated variable, a temperature deviation may remain even in
a steady state and a loop break may be detected.
LBA ON LBA ON LBA OFF LBA OFF
(1)
(2) (3) (4) (5) (6) (7)
Set point
LBA detec-
tion time
Area where LBA
is not detected LBA detection
time
LBA detection
time
LBA detection
time
LBA band LBA band
LBA band
LBA level
LBA level