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PLC User's Manual - Analog Control Edition
PID Instruction (FNC 88)
M-3
1 Outline
1.1 Outline of function
K
FX
3U
-4AD-PNK
-ADP
L
FX
3U
-4AD-TC
-ADP
M
PID Instruction
(FNC 88)
1. Outline
This chapter describes the outline of PID instruction (FNC88) for the FX3U/FX3UC/FX3G Series PLC.
1.1 Outline of function
The PID instruction requires the system to calculate the output (MV) value from the measured (PV) value.
Through combining the P (proportional) action, I (integral) action, and D (derivative) action the target (SV)
value can be obtained. See diagram below.
1) Alarm output function
The alarm function can be set for input variation (measured value) or output variation (value).
2) Setting limit values
The upper limit and lower limit can be set for the output value.
3) Auto-tuning function
The proportional gain (KP), integral time (TI) and differential time (TD) can be set automatically for both
the limit cycle method and step response method.
4) Operation method of the PID instruction
Both PID speed type operation and measured value differential type operation are executed.
FX
3U
/FX
3UC
/FX
3G Series PLC
Controlled
object
Measured value (PV)
Output value (MV)
Target value
(SV)
PID Instruction