Mitsubishi Electric MELSEC-Q/L - Page 742

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7 APPLICATION INSTRUCTIONS
7.18 PID Instruction
Derivative time (T
D
): (S3)+6
Setting range: 0 to 32767 [10ms]
PID control: derivative operation
PID control is used to sensitively react to changes caused in the process value (PV) by disturbance and minimize the
changes.
• Increasing the derivative time (T
D
) enhances the movement to prevent the controlled system from varying greatly due to
disturbance.
Ex.
PID operation in heating (reverse action)
TD3 > TD2 > TD1
MV
Disturbance
T
D3 (PID action)
T
D1 (PID action)
T
D2 (PID action)
Error (EV)
Time
Time
T
D3 (PID action)
T
D1 (PID action)
T
D2 (PID action)
Error
TD3 > TD2 > TD1
TD3 > TD2 > TD1
MV
Change caused by disturbance
Response to the disturbance
T
D3 (PID action)
T
D1 (PID action)
T
D2 (PID action)
PI action (D action not performed)
SV
Time
Time
PI action (D action not performed)
T
D1 (PID action)
T
D2 (PID action)
T
D3 (PID action)
Temperature