Mitsubishi FX3U-4AD User Manual page 442

FX /FX /FX PLC User's Manual - Analog Control Edition
3G 3U 3UC
PID Instruction (FNC 88)
3.2.2 Operation setting (ACT):(S3)+1
1. Forward operation or backward operation:
Select the PID control direction (forward or backward).
• During auto-tuning for the limit cycle method
It is necessary to set the PID control direction (forward or backward) for auto-tuning.
• During auto-tuning for the step response method
The PID control direction (forward or backward) is not required as, the direction is automatically set when
auto-tuning is complete.
Forward operation:
As the measured value (PV) becomes larger than the target value (SV), the output (MV) increases.
For example, cooling is a forward operation.
<Cooling>
Backward operation:
As the measured value (PV) becomes smaller than the target value (SV), the output (MV) increases.
For example, heating is a backward operation.
<Heating>
Relationship between the forward/backward operation and the output (MV), measured value (PV) and
target value (SV)
The relationship is as follows.
L-10
Setting range: OFF = forward operation, ON = backward operation
+1, bit 0 = 0
S
3
Measured value (PV)
+1, bit 0 = 1
S
3
Measured value (PV)
Target value (SV)
Backward
operation
Measured value (PV)
+1, bit 0
S
3
Target value (SV)
Time
Target value (SV)
Time
Forward
operation
3 Parameter
3.2 Details of Parameters