User Manual

High−level Instructions
3 − 767
3) Derivative operation
Derivative operation generates an output which is proportional to the derivative time of the input.
Output mD
Offset e
Setting signal SV
Measurement
signal PV
+
−
e
mD
mD=TD・
de
dt
Derivative
operation
The advancing characteristic of der ivative control alleviates the adverse effect which the delaying
characteristic of the process exerts on control.
Derivative control grows stronger as the derivative time (Td) is increased.
In the case of pure derivative operation, control can temporarily become ineffective if noise is input, and this
can have an adverse effect on the process being controlled. For this reason, incomplete differential operation
is executed.
e
mD
4) PID operation
PID operation is a combination of proportional, integral, and derivative operation.
Kp
Output MV
Offset e
Setting signal SV
Measurement signal PV
+
−
+
+
+
Integral
operation
Derivative
operation
If the parameters are set to the optimum values, PID control can quickly bring the amount of control to the
target value and maintain it there.