Ransburg Evolver MicroPak Controller A10406 - Manual (Page 21)

MICROPAK GROUNDING
THEORY
Electrical noise refers to stray electrical signals in
the atmosphere at various signal strengths and
frequencies that can affect the operation of elec-
trical equipment. One of the best ways to prevent
this is to shield the equipment and cables with a
continous ground envelope, such that any incident
noise will be conducted to earth ground before it
can affect the circuit conductors.
For conductors inside the Evolver MicroPak
Controller, the grounded enclosure provides this
envelope. For the low voltage cable(s) that run
from the controller to the Evolver spray guns, a
shielded cable has been used. The shield consists
of an overall foiled shield in combination with an
overall braided shield. This provides the most ef-
fective shielding, as the foil covers the “holes” in
the braid, and the braid allows for practical 360°
termination at both ends of the cable.
The AC input cord is not shielded, but instead is
directed to an AC line filter in the 24VDC power
supply as soon as it enters the cabinet. This filter
filters out any noise that comes in on the AC line.
For maximum noise immunity the AC line should
connect to the filter as soon as possible after it
enters the cabinet. Additional noise protection can
be provided by running the AC input line to the
controller in grounded conduit, which is the recom-
mended method and is required by most codes.
For maximum noise protection any user supplied
input/output (I/O) wiring should be made using
shielded cable or conduit which is connected to
earth ground in a continuous 360° fashion at both
ends. The best way to do this is to use a conductive
connector/fitting at each end of the cable/conduit
that makes contact to the shield/conduit in a full
360° circle around the shield/conduit and makes
contact to the grounded enclosure in the same
fashion. Connecting the drain wire of a shield to
a ground point on or in the cabinet (usually re-
ferred to as pigtailing) is not an effective method
of shielding and can actually make things worse
(see Figure 7).
Figure 7: Cable Connection Examples
A special cable grommet fitting has been provided
for I/O connector P3 of the controller (see Figure
4). When the nut is tightened, the spring in the
grommet compresses and makes 360° contact
with the braid of the cable. This electrically con-
nects the cable braid to ground via the connector
housing and controller back panel.
Using the methods described above, the Evolver
MicroPak controller has been successfully tested
to the stringent standards of the Electromagnetic
Compatibility Directive of the European Union.
The results conclude that the Evolver MicroPak
Controller is neither a source of electrical noise
nor affected by electrical noise when the above
methods are utilized.
Evolver MicroPak Controller - Installation
Ransburg
18 LN-9622-00.5