KROHNE CORIMASS MFC 85 Interface EN - Manual (Page 12)

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1. General
The Mass flow Converter, MFC 081/085 with RS 485 interface fitted, is able to communicate
with an external device (PC or other suitable computer system). This option allows data
exchange between PC or computer and single or multiple devices.
The Bus configuration consists of one external device as a master and one or more converters
(MFC 081 or MFC 085) as slaves. For Bus operation the device address and baud rate must
be programmedin the menu 3.11.0 of the MFC 081/085. Devices connected to the Bus must
have different or unique addresses and the same baud rate.
The transmission uses 8 (eight) data bits, even parity and 2 (two) stop bits at a selectable
baud rate of 1200 to 19 200.
2. Technical Specifications
Interface RS 485, potential isolated
Baud rate 1200, 2400, 4800,9600,19200 baud
Maximum participants on Bus 32 per line,master included (may be extended by repeaters)
Coding NRZ bit coding
Address range 0 - 239
Transmission procedure half duplex, asynchronous
Bus access master/slave
Protocol Krohne RS 485 Communication Bus Protocol
(Available as a separate instruction document on request)
Cable screened twisted pair cable
Distances maximum 1.2 km without repeater.
(Dependant on baud rate and cable specifications)
Technical data of the RS 485 interface (according to EIA standards)
Kind of signal transmission: differential
Maximum number of transmitter/receivers: 32
Maximum voltage on driver output: –7 V to +12 V
Minimum voltage on driver output, max.load: U diff > 1,5 V
Maximum input current (off state) –20 to +20 • A
Receiver input voltage –7 V to +12 V
Sensitivity of the receiver –200 mV to +200 mV
Receiver input resistance > 12 k ohm
Short circuit current of transmission < 250 mA