Bender ISOMETER iso1685FR, Manual

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31 iso1685FR(M)_D00002_02_M_XXEN/06.2017
6. Device communication
6.1 Device communication via the BMS bus
6.1.1 RS-485 interface with BMS protocol
The RS-485 interface, galvanically isolated from the device electronics, serves as a physical transmission medi-
um for the BMS protocol (Bender measuring device interface). When one device or other bus-capable devices
are interconnected via the BMS bus in a network, the BMS bus must be terminated at both ends with a 120 Ω
resistor. For this purpose, the device is equipped with the terminating switch RS-485 Term. (off/on).
An RS-485 network that is not terminated is likely to become unstable and may result in malfunctions. Only the
first and last device in one line may be terminated. Stub feeders in the network (if any) must not be terminated.
The length of the stub feeders is restricted to 1 meter.
Abb. 6.1: Wiring and termination of the BMS bus with the device housing
A1 A2 E KE 21 22 24 31 32 34 k l kT IT A B S
RS-485
Term.
off on
CAN 1 CAN 2
I2+ I2- I1+ I1-
K3 K2
11 12 14
K1
I2+ I2- I1+ I1- A B S k I kT IT 31 32 34 21 22 24 11 12 14 E KE A1 A2
A B S
RS-485
Term.
off on
CAN 2
A B S
A B S
CAN 2
A B S
maximum length of the RS-485 network: 1200 m
1. device … device last device
stub feeder
max. 1 m