Mitsubishi Electric MELSEC-Q/L - Page 736

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7 APPLICATION INSTRUCTIONS
7.18 PID Instruction
Action setting (ACT): (S3)+1
■Direct action/reverse action: (S3)+1 Bit 0
Setting range: OFF = direct action/ON = reverse action
Select the direct action or reverse action for the PID control direction.
• In the case of auto tuning (limit cycle method)
For auto tuning, the user needs to set the relevant PID control direction, direct action or reverse action.
• In the case of auto tuning (step response method)
At completion of auto tuning executed in whichever mode, direct action or reverse action mode, setting is made automatically.
[Direct action ((S3)+1 Bit 0 = OFF)]
The manipulated value (MV) increases as the process value (PV) increases more from the set value (SV).
For example, cooling is the direct action.
[Reverse action ((S3)+1 Bit 0 = ON)]
The manipulated value (MV) increases as the process value (PV) decreases more from the set value (SV).
For example, heating is the reverse action.
The following figure shows the relationships between the direct/reverse actions and the manipulated value (MV), process
value (PV), and set value (SV).
PV
SV
Time
Temperature
Temperature
Time
PV
SV
MV
SV
Direct action
PV
Reverse
action