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TB149 Rev1 Troubleshooting Motor/Encoder Problems
Overview
This document will help you in the process of troubleshooting motor/encoder problems It can sometimes
be quite difficult to troubleshoot both motors and encoders because it can be tricky to pinpoint the exact
source of the problem
Troubleshooting
The following table is the suggested procedure for troubleshooting motors and encoders The suspect
motor in each case is called motor/axis "X" and a known good motor/axis is called "Y"
Problem Suggested Test Result Next Step
1 Getting
position errors
on axis/motor X Go to PID
screen and test for
encoder feedback for
axis/motor X If your absolute
position changes when you
turn the motor shaft then you
have encoder feedback Encoder feedback?
Yes Encoder for
motor X is giving
feedback
Go to step 2
No Encoder not
working or bad
cable/connection
Go to step 3
2 Getting
position errors
on axis/motor X
getting encoder
feedback Test for accurate encoder
feedback At the PID
screen
turn motor X one complete
resolution The absolute
position should change by the
number of counts listed in the
motor config menu Correct Encoder
feedback? Yes
Encoder working
correctly
Check PID configuration Do
Autotune If MaxVel value is
abnormal then replace drive If AC
motor System then go to Step 4
No Encoder bad or
bad cable/connection
or bad CPU card
Examine Encoder cable Replace
Encoder Replace CPU card
3 Getting
position errors
on axis/motor X
no encoder
feedback
Examine Encoder cable
cable connections to the
motor and CPU card All Connections
correct
Replace Encoder Replace CPU
card If AC motor system replace
drive
4 If Getting
position errors
on AC motor
system getting
encoder
feedback Go to PID and then DRIVE
screen Perform a MOVE
SYNC ON THE AXIS AT
LEAST FOUR TIMES At some point did the
screen read
TIGHTEN ENCODER
NOW Yes Check power cables and drive
No Power off control and repeat If
Message appears then the Check
motor cables for grounding or miss
wire Replace Encoder If message
does not appear then Align the
encoder Refer to TB166
Document History
Rev1 Created on 2002 10 01 by #000