Emc Installation Guidelines; Hardware Installation; Wiring Connections - Siemens SITRANS RD500 Operating Instructions Manual

EMC INSTALLATION GUIDELINES

Although Siemens Products are 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 a unit may be
different for various installations. Cable length, routing, and shield
termination are very important and can mean the difference between a
successful or troublesome installation. Listed are some EMI guidelines for a
successful installation in an industrial environment.
1. A unit should be mounted in a metal enclosure, which is properly
connected to protective earth.
a. The mounting clip that connects to the DIN rail should have the DIN rail
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 to earth ground (protective earth) at one end where
the unit is mounted.
b. Connect the shield to earth ground at both ends of the cable, usually
when the noise source frequency is over 1 MHz.
c. Connect the shield to common of the module 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 through 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. Also, Signal or
Control cables within an enclosure should be routed as far away as
possible from contactors, control relays, transformers, and other noisy
components.
4. Long cable runs are more susceptible to EMI pickup than short cable runs.
Therefore, keep cable runs as short as possible.

HARDWARE INSTALLATION

SEPARATE BASE
FROM MODULE
1
2
MODULE BASE
WIRING

WIRING CONNECTIONS

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. When wiring the module, use the numbers on the label to identify
the position number with the proper function. Strip the wire, leaving approximately
1/4" (6 mm) of bare wire exposed. Insert the wire into the terminal, and tighten.
7ML19985MB01
5. In extremely high EMI environments, the use of external EMI suppression
6. To protect relay contacts that control inductive loads and to minimize
7. Also care should be taken when connecting input and output devices to
ATTACH THE MODULE BASE
TO THE DIN RAIL
3
4
SITRANS RD500
devices such as Ferrite Suppression Cores for signal and control cables
is effective. The following EMI suppression devices (or equivalent) are
recommended:
Fair-Rite part number 0443167251
TDK part number ZCAT3035-1330A
Steward part number 28B2029-0A0
radiated and conducted noise (EMI), some type of contact protection
network is normally installed across the load, the contacts or both. The
most effective location is across the load.
a. Using a snubber, which is a resistor-capacitor (RC) network or metal
oxide varistor (MOV) across an AC inductive load is very effective at
reducing EMI and increasing relay contact life.
b. If a DC inductive load (such as a DC relay coil) is controlled by a
transistor switch, care must be taken not to exceed the breakdown
voltage of the transistor when the load is switched. One of the most
effective ways is to place a diode across the inductive load. External
diode protection at the load is always a good design practice to limit
EMI. Although the use of a snubber or varistor could be used.
Note: Reference manufacturer's instructions when
installing any EMI suppression device.
the instrument. When a separate input and output common is provided,
they should not be mixed. Therefore a sensor common should NOT be
connected to an output common. This would cause EMI on the sensitive
input common, which could effect the instrument's operation.
ATTACH MODULE TO BASE
5
13
7
1
MODULE BASE
Terminals 13 to 18
Terminals 7 to 12
Terminals 1 to 6
Page 3