Handheld Terminal
CE Conformity, Directives and Standards
User's Manual, Version: 1.3
157
© KEBA 2007
14.3.3.1 Shield connections
The cable shield of the KeTop cable can be considered to be an extension
of the KeTop shielded housing (=printed circuit board) to the shielded hous-
ing of the communication partner (e.g.: PLC). From this it can be deduced
that the shielded connections from the cable shield to the device shields
make a fundamental contribution to the interference immunity of the KeTop.
It is not necessary to wire shielded connections to earth.
The shielding connection in the KeTop is made via the RJ-45 connector in
the connection slot.
Connecting the KeTop via the connection box (e.g. CB211) guarantees
safe shielding protection right through to the communication partner. It is
therefore urgently recommended to use a suitable KEBA connection box.
All connection cables available from KEBA (KeTop TTxxx, KeTop ICxxx,
KeTop XD040 and KeTop CD040) guarantee correct shielding connection.
For self-made cables the following conditions must be met for shielding
data lines:
z
On every connector design (DSUB or RJ-45) the cable shield must be
connected to as large a surface area of the connector housing as pos-
sible.
1
2
1
2
DSUB connector
RJ-45 connector
1 .......... Metallised or metallic housing
2 .......... Connect the shield to a large surface area
Correct shield connection for DSUB and RJ-45 connectors
z
The use of pig tails for contacting the cable shield via plug pins is un-
suitable. The inductivity of such pig tails represents high impedance re-
sistance for higher frequency interference; this means an apparent
break in the cable shield. Interference is then no longer diverted and
works directly on the inner lines.
No pig tails
Insufficient contacting of a cable shield