Circutor DHB Series Manual de usuario descargar pdf (Pagina 36)

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

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Circutor DHB Series Manual de usuario Pagina 36