Mitsubishi Electric MELSEC FX2N-2LC, User Manual

Page: 72 / 100

FX2N-2LC Temperature Control Block Buffer Memory (BFM) 7
7-18
7.2.28 BFM #45 (CH1) and BFM #64 (CH2): AT (auto tuning) bias
In BFM #45, set the AT (auto tuning) bias of CH1. In BFM #64, set the AT (auto tuning) bias of
CH2.
The allowable set range is ± input range span (
°
C /
°
F).
Set the AT bias for control targets in which the measured value (PV) should not exceed the
temperature set value (SV) while auto tuning is performed.
The auto tuning function performs two-position control using the temperature set value (SV),
hunts the measured value (PV), then calculates and sets each PID constant. However, for
some control targets, overshoot caused by hunting is not desirable. Set the AT bias for such a
case. When the AT bias is set, the set value (SV, AT point) with which auto tuning is performed
can be changed.
7.2.29 BFM #46 (CH1) and BFM #65 (CH2): Normal/reverse operation selection
In BFM #46, select the normal or reverse operation of CH1. In BFM #65, select the normal or
reverse operation of CH2.
When BFM #46/#65 is set to "K0", normal operation is selected.
When BFM #46/#65 is set to "K1 (initial value)", reverse operation is selected.
The initial value is "reverse operation" (to control heating).
Table 7.4:
Normal operation (0) When actual temperature is higher than set value To control cooling
Reverse operation (1) When actual temperature is lower than set value To control heating
Temperature
set value (SV)
AT starts.
Time
Measured value (PV)
AT finishes.
Example: When the AT bias is set to "-"
AT point
AT bias