8. PARAMETER DESCRIPTION
IMR02C15-E4
8-109
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 (power controller, 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 Measured 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.
[Alarm action]
LBA determination range: Thermocouple/RTD input: 2 °C [°F] (fixed)
Voltage/Current input: 0.2 % of span (fixed)
Heat control
When the output reaches 0 %
(low limit with output limit function)
When the output exceeds 100 %
(high limit with output limit function)
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 LBA time has passed and the PV
has not risen beyond the alarm determination
range, the alarm will be turned on.
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.
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.
Normally the LBA time of Parameter setting mode should be set to approximately twice the
Integral time.
LBA function is not operative when:
• When AT function is activated.
• When the controller is in STOP mode.
• LBA time is set to “0.”
• LBA function is not assigned to Event 1 (ES1) to Event 4 (ES4).
If the LBA time is too short or does not match the controlled object requirements, LBA may
turn ON or OFF at inappropriate time or remain OFF. Change the LBA time based on the
malfunction.
If the LBA function detects an error occurring in the control loop, but cannot specify the
location, the control loop should be checked. The LBA function does not detect the location
which causes alarm status. If LBA alarm is ON, check each device or wiring in the control
loop.
While the LBA is ON (under alarm status), the following conditions will 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 time.
• The Measured value (PV) enters within the LBA deadband.
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