HBM WE2108 Series, Reference Manual

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WE2108
HBM A1632-2.0 en
3.2.7 RS−232 interface (only RS−232 versions)
Terminal PC board legend Function Standard assignment
of external unit
RS−232 DB25 RS−232 DB9
19 GND Ground Pin7 Pin5
20 Ta TxD Data output to the
external unit (TxD) RxD, Pin3 RxD, Pin2
21 Tb DTR do not connect !
22 Ra RxD Data input from the
external unit (RxD) TxD, Pin2 TxD, Pin3
23 Rb do not connect !
24 GND Ground
TxD TxD
RxD RxD
GND GND
For the communication with an external device its TxD line must be
connected with RxD of the WE2108 and vice versa.
3.2.8 RS−485 interface (only RS−485 versions)
See Reference Manual Part 2 (Description of the commands for computer
integration)
3.2.9 Remarks
For all housing variants, the reference ground (GND) for all signals and
the supply voltage is connected directly to the cable screen connection
in the unit, but not to the housing.
The metal housing of WE2108M / WE2108S is not connected to reference
ground. In order to compensate for potential differences, the metal
housing of WE2108s and WE2108M has to be connected via a low ohmic
compensation conductor with the scale components as well as with the
ground potential of the connected units. This is not necessary if a
potential difference of 35 V is not exceeded.
Up to four load cells of 350 ohms (
w
87 ohms burden) can be connected to
the WE2108. HBM offers junction boxes of the types VKK1−4 or VKK2−6 for
connecting the cables as well as for corner balancing (”corner load adjust-
ment”) for scales with several load cells.
Only high quality, flexible cables with shield may be used for connecting the
load cells. HBM recommends the use of these cables for all connections of
the WE2108. For connection satisfying EMC requirements (EMC = electro-
magnetic compatibility), the cable shield of all cables must have a low−resis-
tance contact to the unit ground, for this purpose the shield must be stripped
to approx. 5 mm and the cable must be fastened with the strain relief clips.