ABB AC 800M, User Manual

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RS485 installation recommendation Section 2 Transmission Technology
32 3BDS009029R5001 B
RS485 installation recommendation
Problems with data transmission in PROFIBUS networks can be attributed to
incorrect wiring or installation. These problems can often be solved using bus test
equipment such as bus monitors, which are able to detect many typical wiring errors
even before commissioning.
The list below helps to build up a RS485 network quick and accurate:
• Only use shielded and twisted-pair wiring as a RS485 bus line.
• Use a PROFIBUS bus connector plug to connect the RS485 bus segment.
• If the module is at the beginning or end of a bus segment, this connector must
have an activated bus terminal resistor combination.
• Ensure that the bus segment connected to the RS485 interface is terminated at
both ends.
• All PROFIBUS bus connector plugs in a network must be securely screwed
onto the RS485 interfaces.
• Attaching or removing the bus connector plugs, inadequately attached bus
connector plugs or loose bus wires within the plug can lead to malfunctions in
the networks.
• Attach or remove the RS485 bus connector plug quickly and without twisting
them.
RS485-IS Transmission technology
The RS485-IS transmission technology is based on RS485 with its fast transmission
rate and simple usage, but additional for installation in intrinsically safe areas.
RS485-IS is specified as a 4-wire medium in protection type EEx-i for use in
potentially explosive areas. Therefore the specified level of power refer to the
safety-relevant maximum values must not be exceeded in either individual devices
or during interconnection in the system. An electrical circuit permits maximum
currents at the specified voltage level. With RS485-IS all stations represent active
sources, which is in contrast to the FISCO model, that only has one intrinsically safe
source. Also it is possible to connect up to 32 devices to the intrinsically safe bus
circuit.