Chapter 10 Troubleshooting
10-8
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10.4 Troubleshooting and Countermeasures
Describes the various circuit example and countermeasure.
10.4.1
Input circuit troubles and corrective actions
Describes the various troubleshooting and its countermeasures.
Condition
Cause
Corrective Actions
Input signal
doesn’t turn
off.
Leakage current of external device
(Such as a drive by non-contact switch)
Input signal
doesn’t turn
off.
(Neon lamp
may be still
on)
Leakage current of external device
(Drive by a limit switch with neon lamp)
y
Connect an appropriate resistor and
capacity, which will make the voltage lower
across the terminals of the input module.
y
CR values are determined by the leakage
current value.
−
Recommended value C : 0.1 ~ 0.47
㎌
R: 47 ~ 120
Ω
(1/2W)
Or make up another independent display
circuit.
Input signal
doesn’t turn
off.
Current leakage due to line capacity of wiring
cable.
y
Locate the power supply on the external
device side as shown below.
Input signal
doesn’t turn
off.
Current leakage of external device (Drive by
switch with LED indicator)
y
Connect an appropriate resistor, which
will make the voltage higher than the OFF
voltage across the input module terminal
and common terminal.
Input signal
doesn’t turn
off.
y
Sneak current due to the use of two different
power supplies.
y
E1 > E2, sneaked.
y
Use only one power supply.
y
Connect a sneak current prevention
diode.
DC
input
L
E
E
C
External device
AC
input
R
Leakage current
DC
input
R
E1
DC
input
L
E
External device
DC
input
R
Leakage current
C
AC
input
R
~
AC
input
External device
~
External device
AC
input
Leakage current
~
C
External device
AC
input
R
Leakage current
~
