Additional 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 the
electrical noise, source or coupling method into the unit may be different for
various installations. Listed below are some additional 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.
a. If the bezel is exposed to high Electro-Static Discharge (ESD) levels,
above 4 Kv, it should be connected to protective earth. This can be done
by making sure the metal bezel makes proper contact to the panel cut-out
or connecting the bezel screw with a spade terminal and wire 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 very electrically noisy 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 to suppress power line
interference. Install them near the power entry point of the enclosure. The
following EMI suppression devices (or equivalent) are recommended:
Ferrite Suppression Cores for signal and control cables:
Fair-Rite # 0443167251 (RLC #FCOR0000)
TDK # ZCAT3035-1330A
Steward #28B2029-0A0
Line Filters for input power cables:
Schaffner # FN610-1/07 (RLC #LFIL0000)
Schaffner # FN670-1.8/07
Corcom #1VR3
Note:
Reference manufacturer’s instructions when installing a line filter.
6. Long cable runs are more susceptible to EMI pickup than short cable runs.
Therefore, keep cable runs as short as possible.
7. Switching of inductive loads produces high EMI. Use of snubbers across
inductive loads suppresses EMI.
Snubbers:
RLC #SNUB0000
WIRING CONNECTIONS
After the unit has been mechanically mounted, it is ready to be wired. All
wiring connections are made on removable plug-in terminal blocks. There is a
separate terminal block for the bottom board (TBA), relay board (TBB), count
inputs (TBC), and optional Serial Communications (TBD). When wiring the
unit, remove the terminal block and use the numbers on the label to identify the
position number with the proper function. Simply strip the wire, leaving
approximately ¼" bare wire exposed (stranded wires should be tinned with
solder). Insert the wire into the terminal and tighten down the screw until the wire
is clamped in tightly. Each terminal can accept up to two 18-gage wires. After the
terminal block is wired, install it in the proper location on the PC board. Wire
each terminal block in this manner.
All conductors should meet voltage and current ratings for each terminal. Also
cabling should conform to appropriate standards of good installation, local codes
and regulations. It is recommended that power supplied to the unit (AC or DC) be
protected by a fuse or circuit breaker.
Phone: 800.894.0412 - Fax: 888.723.4773 - Web: www.clrwtr.com - Email: [email protected]
