Mitsubishi FX3U-4AD User Manual page 441

FX /FX /FX PLC User's Manual - Analog Control Edition
3G 3U 3UC
PID Instruction (FNC 88)
3.2 Details of Parameters
3.2.1 Sampling time (T
Set the cycle time (ms) for the PID operation.
• In the PID control
Set the sampling time longer than the operation cycle of the PLC.
• In the auto-tuning
Set the sampling time to 1,000 ms (= 1 second) or more.
1. Maximum error
The maximum error of the sampling time (T
cycle)."
1) When the sampling time (T
Fluctuation of the maximum error described above may cause a problem.
In such a case, execute the PID instruction in the constant scan mode, or program it in a timer interrupt
routine.
2) When the sampling time (T
A PID operation error (K6740) occurs, however when PID operation is executed, the sampling time (T
equal to the operation cycle of the PLC.
In such a case, use the PID instruction in a timer interrupt (I6
executing the PID instruction.
→ For a detailed description, refer to FX
X000
I610
): (S3)
S
) is from "-(one operation cycle + 1 ms)" to "+(one operation
S
) is a small value
S
) is shorter than one operation cycle of the PLC
S
/FX
3U 3UC
FNC 12
K 0 D107
MOVP
FNC 88
D 0 D 1
PID
Setting range: 1 to 32767 [ms]
to I8 ), and clear
/FX Series Programming Manual - Basic & Applied
3G
S
3 +7 is reset.
(When the interrupt routine is executed for the
first time,the register for internal processing is
cleared by the pulse generation command.)
The PID operation is
D100 D150
executed.
3 Parameter
3.2 Details of Parameters
K
L
) is
S
+7 just before
S
3
Instruction Edition
L-9