Outline; Outline Of Function - Mitsubishi Electric MELSEC-FX3S Series Manual

FX /FX /FX /FX /FX
3S 3G 3GC 3U 3UC
PID Instruction (FNC 88)
1.

Outline

This chapter describes the outline of PID instruction (FNC88) for the FX
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 (K
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 /FX
3S 3G
Target value
(SV)
PLC User's Manual - Analog Control Edition
), integral time (T
P
/FX /FX /FX
Series PLC
3GC 3U 3UC
PID Instruction
/FX
3S
) and differential time (T ) can be set automatically for both
I D
Measured value (PV)
Output value (MV)
1 Outline
1.1 Outline of function
/FX /FX /FX Series
3G 3GC 3U 3UC
Controlled
object
M-3
K
L
M