CIRCUTOR DHB Series - Manual (Page 36)

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Fig. 13. Connection Way of the RS-485 Interface
6. RS-485 INTERFACE
DHB-124 programmable digital meters have serial interface
in RS-485 standards for the communication in computer systems
and with other devices fulfilling Master function. An asynchronous com-
munication character protocol MODBUS has been implemented.
The transmission protocol describes ways of information between
devices through the serial interface.
6.1. Connection Way of the Serial Interface
The RS-485 standard allows to a direct communication of 32 devices
on a single serial link of 1200 m long (at baud rate 9600 b/s). For the
connection of a higher quantity of devices, it is necessary to apply ad-
ditional intermediate-separating systems (e.g. PD51 converter).
The lead of the interface line is presented on the Fig. 4. To obtain a
correct transmission, it is necessary to connect lines A and B in parallel
with their equivalents in other devices. The connection must be made
through a shielded wire. The wire shield must be connected to the pro-
tection terminal in the nearest possible proximity of the meter (connect
DHB-124
DHB-124
DHB-124