Mitsubishi A2USCPU(S1), User Manual

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11. TROUBLESHOOTING
11.4 Fault Examples with I/O Modules
Examples of faults concerning I/O circuits and the corrective actions are explained.
11.4.1 Faults with the input circuit and the corrective actions
Examples of faults concerning input circuits and the corrective actions are explained.
Table 11.2 Faults with the input circuit and the corrective actions
Situation Cause Countermeasure
Example
1
Input signal does not
turn OFF.
• Leak current from input switch
(driven by a contactless switch, etc.)
• Connect an appropriate resistor so that
voltage between the terminals of the input
module is lower than the OFF voltage.
For CR constant,
0.1 to 0.47 F+47 to 120 (1/2W) is recommended.
Example
2
Input signal does not
turn OFF.
• Driven by a limit switch with a neon lamp
• Same as the example 1.
• Or, provide a totally independent display
circuit separately.
Example
3
Input signal does not
turn OFF.
• Line capacity C of the leak current twisted pair
cable due to line capacity of the wiring cable
is about 100PF/m.
• Same as the example 1.
• However, it does not occur when power
supply is on the side of input device as shown
below.
Example
4
Input signal does not
turn OFF.
• Driven by a switch with LED indication
• Connect an appropriate resistance so that
voltage between the terminal of the input
module and the common is lower than the
OFF voltage as shown below.
*
AC input
Input
module
Leakage
current
Power supply
Input
module
AC input
R
AC input
Input
module
Leakage
current
Power supply
AC input
Input
module
Leakage
current
Power supply
AC input
Input
module
Power supply
DC input (sink)
Input
module
Leakage current
DC input (sink)
Input
module
Resister
An example of calculation of resistance to be
connected is provided on the following page.