User`s manual

Troubleshooting I/O circuit troubleshooting
11 – 102
3 Excessive voltage is
applied to load when
output turns off.
(Triac output)
The load (e. g. magnetic valve) contains a rectifier for one
way (diode). The internal capacitor of the output module is
charged by this diode during one sine halfwave. The
resulting voltage at the diode during the other halfwave is
the voltage of the power supply plus the charged voltage of
the capacitor.
(This usage does not pose problems to the output compo-
nents but may deteriorate the diode built in the load, caus-
ing burnout, etc.)
Connect a resistor of several ten k
Ω to
several hundred k
Ω at both ends of the
load.
4 Load does not turn
off. (Triac output)
Leakage current due to the built-in surge suppressor Connect a resistor at both ends of the
load. (If the wiring from the output mod-
ule to the load is long, be careful since
there may be a leakage current due to
the line capacity.)
5 Load does not turn
off. (Triac output)
The load current is lower than the minimum load current of
the output module.
Connect a resistor to both ends of a
load so that the load current is higher
than the minimum load current.
Exam-
ple
Condition Cause Corrective action
Tab. 11-1: Output circuit troubleshooting