Mitsubishi FX3U-4AD User Manual page 435

FX /FX /FX PLC User's Manual - Analog Control Edition
3G 3U 3UC
PID Instruction (FNC 88)
1. Outline
This chapter describes the outline of PID instruction (FNC88) for the FX
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
Target value
(SV)
/FX /FX
3U 3UC 3G Series PLC
PID Instruction
/FX
3U 3UC
Measured value (PV)
Controlled
object
Output value (MV)
1 Outline
1.1 Outline of function
/FX Series PLC.
3G
L-3
K
L