Справочник Пользователя для Siemens 9300
9300 Series User’s Guide
RS-485 Connections
Chapter 5 - Features and Applications
Page 107
RS-485 Connections
Refer to the “Hardware Reference” chapter for the 9300 Series RS-485
specifications. The communication card is designed with optical coupling that
provides full isolation between the RS-485 communication lines and the meter
internal circuitry. This circuitry provides protection from common mode voltages
and incorrect connections. All inputs pass the ANSI/IEEE C37.90-1989 surge
withstand and fast transient tests.
specifications. The communication card is designed with optical coupling that
provides full isolation between the RS-485 communication lines and the meter
internal circuitry. This circuitry provides protection from common mode voltages
and incorrect connections. All inputs pass the ANSI/IEEE C37.90-1989 surge
withstand and fast transient tests.
The communications terminal strip on the rear of the meter shows two
communication ports: COM 1 and COM 2. (The COM 2 port is not available on the
9300.) Up to 32 devices can be connected on a single RS-485 bus. Use a good quality
shielded twisted pair cable for each RS-485 bus, AWG 22 (0.5 mm
communication ports: COM 1 and COM 2. (The COM 2 port is not available on the
9300.) Up to 32 devices can be connected on a single RS-485 bus. Use a good quality
shielded twisted pair cable for each RS-485 bus, AWG 22 (0.5 mm
2
) or larger. The
overall length of the RS-485 cable connecting all devices cannot exceed 4000 ft.
(1219 m). The RS-485 bus may be configured in straight-line or loop topologies.
(1219 m). The RS-485 bus may be configured in straight-line or loop topologies.
Straight Line Topology
Loop Topology
General Bus Wiring Considerations
Devices connected on the bus, including the meter, converter(s) and other
instrumentation, must be wired as follows:
instrumentation, must be wired as follows:
The shield of each segment of the RS-485 cable must be connected to ground at
one end only.
one end only.
Isolate cables as much as possible from sources of electrical noise.
Use an intermediate terminal strip to connect each device to the bus. This allows
for easy removal of a device for servicing if necessary.
for easy removal of a device for servicing if necessary.
SHLD
RS-232 to
RS-485
Converter
Termination
Resistor
+
SHLD
+
SHLD
+
SHLD
+
SHLD
+
SHLD
R
T
SHLD
+
R
T
-+
COM
RS-485
SH + -
+
SHLD
+
SHLD
SHLD
+
SHLD
+
SHLD
Termination
Block
+
SHLD
SHLD
+
SHLD
RS-232 to
RS-485
Converter
-+
COM
RS-485
SH + -