54
Output Loads Be sure to take appropriate measures when any electrical device likely to
produce noise is connected to the CPU as a load. For example, electromag-
netic relays and valves generating noise of more than 1,200 V require noise
suppression. For AC–operated noise sources, connect a surge suppressor in
parallel with the coil of each device. For DC–operated noise sources, con-
nect a diode in parallel with the coil of each device. When mounting a CPU
and an Expansion I/O Unit on a control panel, be sure to completely ground
the intermediate mounting plate. The mounting plate must be finished with
high–conductivity plating to ensure noise immunity.
RR
–
+
Surge
suppressor
AC power source DC power source
Diode
3–5 Inspection
In order for your PC to continue operating at optimum condition, periodic in-
spections are necessary. The main components of the PC are semiconduc-
tors and have a long service life, but, depending on the operating environ-
ment, there may be more or less deterioration of these and other parts. A
standard inspection schedule would be once every six months to one year,
but more frequent inspections may be advisable depending on the operating
environment. Try to maintain the inspection schedule once it has been set.
Check to be sure that the power supply, ambient temperature, humidity, and
so on, are within the specifications (see Appendix B). Be sure that there are
no loose screws in any of the Units and that all battery and cable connections
are secure. Clean any dust or dirt that has accumulated. Check all fuses, re-
lays, and other replaceable parts.
Inspection Section 3–5
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