Mitsubishi Electronics MELSEC-F Manuel D’Utilisation

6 Troubleshooting

FX

3G

/FX

3U

/FX

3UC

 PLC User's Manual - Analog Control Edition

PID Instruction (FNC 88)

When an error occurs in the set value of a control parameter or the data acquired during the PID operation,
the operation error flag M8067 turns ON, and a corresponding error code is stored in D8067.

6730

Incorrect sampling time (T

S

) (T

S

 

≤ 0)

<PID operation is stopped.>
A data error has occurred in the set value in a control parameter 
or in the middle of PID operation.
Check the parameters.

6732

Incorrect input filter constant (

α)

(

α < 0 or 100 ≤ α)

6733

Incorrect proportional gain (K

P

) (K

P

 < 0)

6734

Incorrect integral time (T

I

) (T

I

 < 0)

6735

Incorrect derivative gain (K

D

)

(K

D

 < 0 or 201 

≤ K

D

)

6736

Incorrect derivative time (T

D

) (T

D

 < 0)

6740

Sampling time (T

S

) 

≤ Operation cycle

<Auto-tuning is continued.>
The operation is continued in the condition "sampling time (T

S

) 

= cyclic time (operation cycle)."

6742

Variation of measured value exceeds limit.
(UPV < 

−32768 or +32767 < UPV)

<PID operation is continued.>
The operation is continued with each parameter set to the 
maximum or minimum value.

6743

Deviation exceeds limit.
(EV < 

−32768 or +32767 < EV)

6744

Integral result exceeds limit.
(Out of range from 

−32768 to +32767)

6745

Derivative value exceeds limit due to derivative gain
(K

D

).

6746

Derivative result exceeds limit.
(Out of range from 

−32768 to +32767)

6747

PID operation result exceeds limit.
(Out of range from 

−32768 to +32767)

6748

PID output upper limit set value < PID output lower limit
set value

<Output upper limit value and output lower limit value are 
exchanged for each other. 

→ PID operation is continued.>

Check whether the target settings are correct.

6749

Abnormal PID input variation alarm set value or output
variation alarm set value (Set value < 0)

<Alarm output is not given. 

→ PID operation is continued.>

Check whether the target settings are correct.

6750

<Step response method>
Improper auto-tuning result

<Auto-tuning is finished. 

→ PID operation is started.>

• The deviation at start of auto-tuning is 150 or less.
• The deviation at end of auto-tuning is 1/3 or more of the 

deviation at start of auto-tuning.

Confirm the measured value and target value, and then execute 
auto-tuning again.

6751

<Step response method>
Auto-tuning operation direction mismatch

<Auto-tuning is forced to finish. 

→ PID operation does not 

started.>
The operation direction estimated from the measured value at 
the start of auto-tuning was different from the actual operation 
direction of the output during auto-tuning.
Correct the relationship among the target value, output value 
for auto-tuning and measured value, and then execute auto-
tuning again.