18
PW20i
HBM
A1269-2.0 en/de/fr
7
Interfaces
ATTENTION
The PW20i interface driver relates to GND. The Master interface driver
must also relate to this GND.
A shielded cable must be used as the bus cable. The shield should
always be connected to the housing at both ends. The shield of the
PW20i cable is electrically connected to the measuring body.
Should it be necessary, a separate cable can be used to establish
potential equalization between the PW20i and the (PC/PLC) master
(earthing concept). Cable shielding must not be used for this potential
equalization.
7.1
RS-232 / RS-485 4-wire interfaces (UART)
The PW20i load cells are delivered as required, either with an RS-232- or
RS-485 4-wire interface. Baud rates of 1200 – 115200 Baud can be set for
both interfaces. The ground reference for all interface signals is based on the
power supply ground (GND) of the PW20i load cell.
The RS-232-interface is only suitable for a point to point connection (one
PW20i load cell to one interface). Only the signals RxD ( Receive Data ), TxD
( Transmit Data ) and GND1 are required.
TxD
TxD
For communication with an external device
RxD
RxD
the TxD line must be connected to the RxD of the PW20i
GND
GND
and vice−versa.
Fig.7.1
Schematic connection of the RS-232 interface
Figure 7.2 shows the necessary connections (RS-232 version) for connecting
to a computer.
12...30 V
Fig. 7.2
Connection of one PW20i to the supply voltage and a computer via an
RS-232 interface
