Bronkhorst EL-FLOW Prestige - Manual (Page 20)

Bronkhorst High-Tech B.V.
EL-FLOW Prestige 9.17.084 20
3.5 Basic RS485 (FLOW-BUS/Modbus) operation
This section is limited to RS485 FLOW-BUS or Modbus communication. For communication through other field bus interfaces see
section 3.6.
FLOW-BUS or Modbus communication is available only if either the FLOW-BUS or Modbus RJ-45 connector on top of the
instrument is present, or if the 9-pin sub-D side connector is set for FLOW-BUS or Modbus communication. The label at the back of
the instrument indicates the factory settings of the connector pinning.
FLOW-BUS
FLOW-BUS is a Bronkhorst designed field bus, based on RS485 technology, for digital communication between devices, offering the
possibility of host-control by a pc.
Characteristics:
Baud rates of 187500 (default) or 400000 Baud
+15…24 Vdc supply voltage
Easy installation and communication with other Bronkhorst devices
Automatic node search and bus optimization (gap fixing)
PC communication via (local host) FLOW-BUS – RS232 interface
Connection of max. 120 instruments on a single bus
Maximum bus length: 600 m
See document 9.17.024 for more information about FLOW-BUS communication.
Modbus
Modbus is a 3-wire, RS485-based field bus communication system for parameter value exchange. In this system each instrument/
device is equipped with a micro-controller for its own dedicated task but also for exchanging parameter value information with
other devices connected to the same Modbus system. In a Modbus system Bronkhorst instruments always serve as Modbus slaves.
There is no mutual communication between Modbus slaves, only between master and slave. The master device is for example a pc.
Characteristics:
Several selectable baud rates between 9600 and 256000 Baud (default: 19200 Baud)
+15…24 Vdc supply voltage
connection of max. 247 instruments on a single bus
supports RTU and ASCII protocols
See document 9.17.035 for more information about Modbus communication.
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More detailed information about Modbus can be found at http://www.modbus.org or any website of the (local)
Modbus organization of your country (when available).