8. ENGINEERING MODE
IMR01N12-E7
81
Continued from the previous page.
Control loop break alarm (LBA)
The Control loop break alarm (LBA) function is used to detect a load (heater) break or a failure in the external
actuator (magnet relay, etc.), or a failure in the control loop caused by an input (sensor) break. The LBA function
is activated when control output reaches 0 % (low limit with output limit function) or 100 % (high limit with
output limit function). LBA monitors variation of the
M
easured value (PV) for the length of LBA time. When
the LBA time has elapsed and the PV is still within the alarm determination range, the LBA will be ON.
The LBA function produces the alarm when any of the following conditions occurs.
LBA determination range: TC/RTD input: 2
C [2
F] (fixed)
Pressure sensor input and Voltage/Current input:
0.2 % of input span (fixed)
When the control output reaches 0
%
(low limit with output limit function)
For direct action:
When the LBA time has passed and the PV has not risen beyond the alarm
determination range, the alarm will be turned on.
For reverse action: When the LBA time has passed and the PV has not fallen below the alarm
determination range, the alarm will be turned on.
When the output exceeds 100
%
(low limit with output high function)
For direct action:
When the LBA time has passed and the PV has not fallen below the alarm
determination range, the alarm will be turned on.
For reverse action: When the LBA time has passed and the PV has not risen beyond the alarm
determination range, the alarm will be turned on.
If the Autotuning function is used, the LBA time is automatically set twice as large as the Integral
time. The LBA setting time will not be changed even if the Integral time is changed.
LBA function is not operative when:
AT function is activated.
T
he controller is in STOP mode.
LBA function is set to “OFF.”
LBA function is not assigned to Event (ES3) or Event 4 (ES4).
The LBA function does not detect a location which causes alarm status. If LBA alarm is ON, check
each device or wiring of the control loop.
While the LBA is ON (under alarm status), the following conditions cancel the alarm status and LBA
will be OFF:
The Measured value (PV) rises beyond (or falls below) the LBA determination range within the
LBA setting time.
The Measured value (PV) enters within the LBA deadband.