Absolute Encoder
Position
Difference Error
(The position
saved in the host
controller when
the power was
turned OFF is
different from the
position when the
power was next
turned ON.)
Noise interference due to improper
encoder cable specifications
The encoder cable must be tinned
annealed copper twisted-pair or
shielded twisted-pair cables with a
core of 0.12 mm
2
min.
Use encoder cable with the speci-
fied specifications.
Noise interference due to length of
encoder cable.
Check the encoder cable length.
The encoder cable length must be
no more than 20 m.
Noise interference due to damaged
encoder cable
Check if the encoder cable is bent or
if its sheath is damaged.
Replace the encoder cable and cor-
rect the encoder cable layout.
Excessive noise interference at the
encoder cable
Check if the encoder cable is bun-
dled with a high-current line or near
high-current line.
Change the encoder cable layout so
that no surge is applied.
FG potential varies because of
influence of machines such as weld-
ers at the servomotor.
Check if the machines are correctly
grounded.
Ground machines correctly, and
prevent diversion to the FG at the
PG side.
SERVOPACK pulse counting error
due to noise interference
Check if there is noise interference
on the input/output signal line from
the encoder.
Take measures against noise in the
encoder wiring.
Excessive vibration and shock to
the encoder
Check if vibration from the machine
occurred or servomotor installation
is incorrect (mounting surface accu-
racy, fixing, alignment, etc.).
Reduce vibration from the machine,
or secure the servomotor installa-
tion.
An encoder fault occurred. − Replace the servomotor.
A SERVOPACK fault occurred.
(The pulse count does not change.)
− Replace the SERVOPACK.
Host controller multi-turn data read-
ing error
Check the error detection at the host
controller.
Correct the error detection section
of the host controller.
Check if the host controller is exe-
cuting data parity checks.
Execute a multi-turn data parity
check.
Check noise in the input/output sig-
nal line between the SERVOPACK
and the host controller.
Take measures against noise, and
again execute a multiturn data par-
ity check.
Overtravel (OT)
Forward or reverse run prohibited
signal is input.
Check the external power supply
(+24 V) voltage for the input signal.
Correct the external power supply
(+24 V) voltage.
Check if the overtravel limit switch
operates properly.
Correct the overtravel limit switch.
Check if the overtravel limit switch
is wired correctly.
Correct the overtravel limit switch
wiring.
Forward or reverse run prohibited
signal malfunctioning.
Check the fluctuation of the input
signal external power supply (+24
V) voltage.
Stabilize the external power supply
(+24 V) voltage.
Check if the overtravel limit switch
operates correctly.
Stabilize the operation of the over-
travel limit switch.
Check if the overtravel limit switch
wiring is correct. (check for dam-
aged cables or loose screws.)
Correct the overtravel limit switch
wiring.
Incorrect forward or reverse run
prohibited signal (P-OT/N-OT)
allocation (parameters Pn50A.3,
Pn50B.0)
Check if the P-OT signal is allo-
cated in Pn50A.3.
If anot
her signal is allocated in
Pn50A.3, select P-OT.
Check if the N-OT signal is allo-
cated in Pn50B.0.
If another signal is allocated in
Pn50B.0, select N-OT.
Incorrect servomotor stop method
selection
Check Pn001.0 and Pn001.1 when
the servomotor power is OFF.
Select a servo mode stop method
other than "coast to stop."
Check Pn001.0 and Pn001.1 when
in torque control.
Select a servo mode stop method
other than "coast to stop."
Problem Probable Cause Investigative Actions Corrective Actions
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