User Manual

Installation and operating instructions BM 70 A/P Page: 12 11/00
Transmission rate: 1200 to 38400 bauds
Address: 0 to 255
Protocols: KROHNE Protocol, HART
®
, Modbus RTU (from firmware
V.3.02/4.02)
Additional information: see "BM 70 A/P Communication RS 485"
instructions
Additional current output: The current output is conductively coupled to the RS 485 interface.
Technical data: see Section 4.5
Note: Switching contact and digital input are not available. However, the
current output can be configured as a switching output.
Various bus configurations
A) Connection of a BM 70 A/P as a single RS 485 user:
RS485 connection must
be terminated with 120 ohms
(if necessary insert resistor
between A and B
)
Computer
system
Bus line (2 shielded wires)
with termination
resistance
120 ohms
B) Connection of several BM 70 A/P in the RS 485 bus system via stubs to the bus cable:
Computer
system
...........
RS485 connection must
be terminated with 120 ohms
(if necessary insert resistor
between A and B)
Bus line (2 shielded wires)
with termination
resistance
120 ohms
without
resistance
termination
without
resistance
termination
without
resistance
termination
C) Connection of several BM 70 A/P in the RS 485 bus system, with bus cable looped through to
further field instruments:
...........
with termination
resistance
120 ohms
without
resistance
termination
without
resistance
termination
without
resistance
termination
Bus line (2 shielded wires)
Computer
system
RS485 connection must
be terminated with 120 ohms
(if necessary insert resistor
between A and B)
Notes:
• If other devices are operated together with the BM 70 A/P Level-Radar on one bus, all devices
must use the same Communications protocol (e.g. ModBus devices of different makes or BM 70
A/P and TTM 70 with KROHNE Protocol).
• When "HART
®
" is set as the protocol type, use only the protocol in keeping with the "HART
®
Specification". The "Hardware Implementation RS 485" does not conform to the HART
®
Standard
(see Sections 4.2 and 4.3).