Mitsubishi Electric A173UHCPU User Manual page 128

5. INSPECTION AND MAINTENANCE
Symptom
Input signal does not
turn OFF
Input signal does not
turn OFF
Input signal does not
turn OFF
Input signal does not
turn OFF
(9) Possible Problems with I/O Modules
This section describes possible problems with input and output circuits, and what to
do about them.
(a) Troubleshooting input circuits
Table 5.7 describes problems and corrective actions for input circuits.
Table 5.7 Troubleshooting Input Circuits
Cause
• Current leakage through input switch.
(Driven using a contactless switch, etc.)
C
Leak current
R
Power supply
• Driven using a limit switch with neon lamp.
Leak current
Power supply
• Leak current due to line capacity of wiring. Line
capacity (C) of twisted-wire pair is approx. 100
pF/m.
Leak current
Power supply
• Driven using a limit switch with LED indicator.
Leak current
• Connect an appropriate resistor to lower the
voltage between the input module terminals
below the OFF voltage.
AC input
Input module
CR constant : 0.1 to 0.47
W) recommended
• See Problem 1, above.
• Alternatively, provide a separate, independent
AC input
display circuit.
Input module
• See Problem 1, above.
• However, this problem does not arise when the
power supply is on the input equipment side.
AC input
Input module
• Connect an appropriate resistor to lower the
voltage between the input module terminal and
DC input (sink)
common terminal below the OFF voltage, as
shown below.
Input module
* The method of calculating the resistor to
connect is shown on the next page.
5 − 17
Corrective Action
AC input
C
Input module
R
Power supply
F + 47 to 120
AC input
Input module
Power supply
DC input (sink)
Resistor
Input module
(1/2