Chapter 12. TROUBLE SHOOTING
12 - 8
12.4 Troubleshooting Examples
Possible troubles with various circuits and their corrective actions are explained.
12.4.1 Input circuit troubles and corrective actions
The followings describe possible troubles with input circuits, as well as corrective actions.
Condition
Cause
Corrective Action
Input signal close not
turn OFF
Leakage current of external device
(such as a drive by non-contact switch)
Input signal does not
turn OFF
Leakage current of external device
(Drive by a limit switch with neon lamp)
•
Connect an appropriate register and
capacity which will make the voltage
across the terminals of the input module
lower than
•
C and R values are determined by the
leakage current value
- Reminded value C : 0.1 ~ 0.47
㎌
R : 47 ~ 120
Ω
(1/2W)
Or make up another independent display
circuit
Input signal does not
turn OFF
Leakage current due to line capacity of
wiring cable
•
Power supply is located on the
external device side as shown below
Input signal does not
turn OFF
Leakage current of external device
(Drive by switch with LED indicator)
•
Connect an appropriate register which
will make the voltage across input
module terminal and common higher
than the OFF voltage, as shown below
Input signal does not
turn OFF
•
Sneak current due to the use of two
different power supplies
•
E1
>
E2, Sneaked
•
Use only one power supply
•
Connect a sneak current prevention
diode, as shown below