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PLC User's Manual - Analog Control Edition
PID Instruction (FNC 88)
M-29
6 Troubleshooting
6.1 Error Codes
K
FX
3U
-4AD-PNK
-ADP
L
FX
3U
-4AD-TC
-ADP
M
PID Instruction
(FNC 88)
Caution
With regard to the measured value (PV) in PID, normal measurement data should be read before PID
operation begins.
Especially when the PID operation is executed to the input value in an analog input block, pay attention to the
conversion time.
6752
<Step response method>
Improper auto-tuning operation
<Auto-tuning is finished. → PID operation is not started.>
Because the set value fluctuated during auto-tuning, auto-
tuning was not executed correctly.
Set the sampling time to a value larger than the output change
cycle, or set a larger value to the input filter constant.
After changing the setting, execute auto-tuning again.
6753
<Limit cycle method>
Abnormal output set value for auto-tuning
[ULV (upper limit) ≤ LLV (lower limit)]
<Auto-tuning is forcibly finished. → PID operation is not
started.>
Check whether the target settings are correct.
6754
<Limit cycle method>
Abnormal PV threshold (hysteresis) set value for auto-
tuning (SH
PV < 0)
6755
<Limit cycle method>
Abnormal auto-tuning transfer status
(Data of device controlling transfer status is abnormally
overwritten.)
<Auto-tuning is forcibly finished. → PID operation is not
started.>
Verify that devices occupied by PID instruction are not
overwritten in the program.
6756
<Limit cycle method>
Abnormal result due to excessive auto-tuning
measurement time (τon > τ, τon < 0, τ < 0)
<Auto-tuning is forcibly finished. → PID operation is not
started.>
The auto-tuning time is too long.
Increase the difference (ULV - LLV) between the upper limit and
the lower limit of the output value for auto-tuning, set a smaller
value to the input filter constant (α), or set a smaller value to the
PV threshold (SH
PV) for auto-tuning, and then check whether
the result is improved.
6757
<Limit cycle method>
Auto-tuning result exceeds proportional gain. (K
P = Out
of range from 0 to 32767)
<Auto-tuning is finished (K
P = 32767). → PID operation is
started.>
The variation of the measured value (PV) is small compared
with the output value. Multiply the measured value (PV) by "10"
so that the variation of the measured value will increase during
auto-tuning.
6758
<Limit cycle method>
Auto-tuning result exceeds integral time.
(T
I = Out of range from 0 to 32767)
<Auto-tuning is finished (K
P = 32767). → PID operation is
started.>
The auto-tuning time is too long.
Increase the difference (ULV - LLV) between the upper limit and
the lower limit of the output value for auto-tuning, set a smaller
value to the input filter constant (α), or set a smaller value to the
PV threshold (SH
PV) for auto-tuning, and then check whether
the result is improved.
6759
<Limit cycle method>
Auto-tuning result exceeds derivative time.
(T
D = Out of range from 0 to 32767)
Error
code
Error description Action