Omron EJ1 User Manual page 119

Using the Loop Break Alarm (LBA)
Determining the LBA
Detection Time
1,2,3...
Operating Conditions
98
• Automatic Settings
The LBA detection time is set automatically by autotuning.
(It is not set automatically for heating/cooling control.)
If the optimum LBA detection time is not obtained by autotuning, set the
LBA Detection Time parameter.
• Manual Settings
To manually set the LBA detection time, set the LBA Detection Time pa-
rameter to twice the LBA reference time given below.
(1) Set the output to the maximum value.
(2) Measure the time required for the width of change in the input to reach
the LBA band.
Measurement time:
Temperature
Tm
LBA Detection Time = Tm × 2
(3) Set the LBA Detection Time parameter to two times the measured
time.
• The LBA operates when one of the alarm types is set to LBA.
• Loop burnout alarms are not detected during SP ramping.
• Loop burnout alarms are not detected during autotuning, manual opera-
tion, or while stopped.
• If the LBA Detection Time, LBA Level, LBA Band, and PID settings are
not appropriate, alarms may be detected inappropriately or alarms may
not be output when necessary.
• Loop burnout alarms may be detected if unexpectedly large disturbances
occur continuously and a large deviation does not decrease.
• If a loop burnout occurs when the set point is near the ambient tempera-
ture, the temperature deviation in a steady state may be less than the LBA
level, preventing detection of the loop burnout.
• 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 burnout may be detected.
• Detection is not possible if a fault occurs that causes an increase in tem-
perature while control is being applied to increase the temperature (e.g., a
solid-state relay short-circuit fault).
• Detection is not possible if a fault occurs that causes a decrease in tem-
perature while control is being applied to decrease the temperature (e.g.,
a heater burnout fault).
Section 4-6
PV
LBA Band
MV=100%
Time