Communication With The Field Instruments Using Operator And Monitoring Stations; Serial Data Transmission With Rs 485 - ABB MAG-SM Instruction Bulletin

Electromagnetic Flowmeter Converter
Data Link Test
Before initiating the test connect the transmitter to the receiver
at the connection terminals. The computer sends 1000
ASCII-Code 31 hex characters and monitors the received
characters. On the left side of the display the number of
characters sent is displayed. On the right side the number of
characters received is displayed. After 1000 characters are
transmitted the computer no longer monitors the received
characters but continues to send the 31 Hex character until the
C/CE key is pressed.
Select Data Link and press ENTER. The test runs
automatically.
Note: No automatic return to process metering. Terminate
using C/CE key.
Select Fout, press ENTER and enter the desired value in Hz.
Monitor the ouptut value at terminals 8D and 31 (TP 14 and 31
in the 19"-Design) for agreement with the entered value.
Frequency range from -13000 Hz to 13000 Hz. For positive
frequency value entries (flowrate 100 % = 10 kHz) the forward
direction totalizer pulses can be monitored (consider the
totalizer settings; pulse factor, pulse width and totalizer units) at
terminals V1 - V2 (if testing with a simulator, at jacks 9/11). For
negative frequency value entries (with a minus sign) the
reverse flow direction totalizer pulses can be monitored at
terminals V3 - V4 (if testing with a simulator, at jacks 9/11R).
Note: No automatic return to process measurements.
Terminate by pressing C/E-key.
Select Display and press ENTER. The converter writes the
numbers 0 to 9 and the letters A to F in the 1st and 2nd lines of
the display. Visually monitor for proper operation of the dot
matrix.
Select Ext. Zero Return and press ENTER. Jumper input G2
to 22 or U2 to 22 (note switch S902 setting on the connection
board), the converter responds off/on.
Note: No automatic return to process measurements.
Terminate by pressing C/E-key.
Select Totalizer Reset and press ENTER. Jumper input U2 to
31 or G2 to 31 (note switch S902 setting on the connection
board), tne converter responds off/on.
Note: No automatic return to process measurements.
Terminate by pressing C/E-key.
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5.5 Communication with the Field Instruments
Using Operator and Monitoring Stations
Two different communication technologies are available for
data exchange between the MAG-SM electromagnetic
flowmeter and a process control system, computer, PC or SPC.
A special RS 485/Profibus DP data link option is available for
the converter or a HART-Protocol option which does not require
any additional installation expenses.

5.5.1 Serial Data Transmission with RS 485

All parameter settings, measurement values such as the
instantaneous flowrate and totalizer value, as well as system
monitoring can be accessed during on-line operation. From a
PC or a direct connection to the converter the converter can
also be reconfigured.
A bus system can be structured using the serial RS 485 data
link. Distances up to 1200 m are possible between the
electromagnetic flowmeter converter and the process control
device. Up to 32 instruments can be connected to a single bus
and can be operated on-line.
RS 485
Level = 5 V. Input impedance: ≥ 12 k
Cable length ≤ 1200 m,
Baudrate: 110-9600 Baud, 14400/28800 Baud.
Max. 32 instruments in parallel on a single bus. A shielded data
cable with individually twisted pairs is recommended.
Terminals V1, V2, V3, V4 Function T-, T+, R-, R+
No. 1
RS 485
4
No. 32
RS 485
Fig.11 Communication with a RS 485 Data Link
Three software data link protocols and a printer protocol are
available.
Communication Protocol ASCII
Communication is always inititated by the host computer. The
converter responds only to the specific command sent from the
host computer.
Converter data can be accessed (Monitor Mode) or
reconfigured (Programming Mode). ASCII information is
described in a separate "ASCII-Communication" document.
Ω
,
Serial
Data Link
RS 485