Red Lion PCU - Manual (Page 15)

EMC INSTALLATION GUIDELINES
Although this unit is designed with a high degree of immunity to
ElectroMagnetic Interference (EMI), proper installation and wiring methods
must be followed to ensure compatibility in each application. The type of
electrical noise, source or coupling method into the unit may be different for
various installations. In extremely high EMI environments, additional
measures may be needed. The unit becomes more immune to EMI with fewer
I/O connections. Cable length, routing and shield termination are very
important and can mean the difference between a successful or a troublesome
installation. Listed below are some EMC guidelines for successful
installation in an industrial environment.
1. The unit should be mounted in a metal enclosure, which is properly
connected to protective earth.
2. Use shielded (screened) cables for all Signal and Control inputs. The shield
(screen) pigtail connection should be made as short as possible. The
connection point for the shield depends somewhat upon the application.
Listed below are the recommended methods of connecting the shield, in
order of their effectiveness.
a. Connect the shield only at the panel where the unit is mounted to earth
ground (protective earth).
b. Connect the shield to earth ground at both ends of the cable, usually
when the noise source frequency is above 1 MHz.
c. Connect the shield to common of the unit and leave the other end of the
shield unconnected and insulated from earth ground.
3. Never run Signal or Control cables in the same conduit or raceway with AC
power lines, conductors feeding motors, solenoids, SCR controls, and
heaters, etc. The cables should be run in metal conduit that is properly
grounded. This is especially useful in applications where cable runs are
long and portable two-way radios are used in close proximity or if the
installation is near a commercial radio transmitter.
4. Signal or Control cables within an enclosure should be routed as far away as
possible from contactors, control relays, transformers, and other noisy
components.
5. In extremely high EMI environments, the use of external EMI suppression
devices, such as ferrite suppression cores, is effective. Install them on
Signal and Control cables as close to the unit as possible. Loop the cable
through the core several times or use multiple cores on each cable for
additional protection. Install line filters on the power input cable to the unit
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Figure 6, Hardware