Mitsubishi FREQROL-SFJ Maintenance Manual page 115

Cause
"Speed detection" Signal on CH31 and 32 (CH23
signal distorted
by noise
S-analog speed
reference signal
distorted by
noise.
Trouble with
motor built-in
encoder
Checkup
for common) of card SFJ-CA1
is distorted by noise.
Signal on CH30 (CH23 for com-
Signals on CH31 and 32(CH23
for common) of card SFJ-CA1
do not offset accurately.
Normal waveform
Peak voltage of signal is not
within t1.5V.
Remedy
Shield the cable
between CON2 and
motor built-in
encoder (without
discontinuity).
Use a cable of
larger size for mo-
tor.
Shield the signal
line properly.
Replace the motor
built-in encoder.