6.2 Specifications and Configurations
6-7
6
(4) Node Shielding
Node shielding is DC isolated from port to port and from local node chassis, as well as from ground and power
signals. (Molex offers an insulated screened connector: PN 85504.) This prevents currents at DC or main fre-
quency from circling the ring, or coming back via some system ground path. The shields are AC coupled via
capacitors (one for each port) to a nearby earth point on the node and/or machine chassis. This capacitor reduces
EMI by dumping high frequency energy to the earth ground. The cable shields are also tied to isolated plane sec-
tions (one for each port) on the node PCB to minimize EMI.
6.2.4 Grounding
SynqNet provides grounding of its communication lines through the connectors. Each connection includes
ground lines for the transmit line and the receive line, as well as earth ground.
For proper machine grounding details, see section 5.4.2 Wiring for Noise Control.
OUT PORT
IN PORT
Node Connector
(Tied to cable shell)
Cable Shell
(Tied to shield)
Cable Shield
Twisted Pair
(one shown)
Chassis or Bracket Isolated
from Connector
C1
C4
D
SD SD
C2 C3
D
S1
S1
S1
C5 C6
R1
R1
R2
AC (Capacitor) coupled to
Earth GND or Digital GND
ISOLATED PLANE
SHIELD GND 50
ISOLATED PLANE
SHIELD GND 51
SIEPS80000025.book 7 ページ ２００４年１０月２５日 月曜日 午前１１時５７分
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