Campbell Scientific MD485 RS-485 Multidrop Interface - Manual (Page 8)

MD485 RS-485 Multidrop Interface
3. System Components
3.1 MD485 RS-485 Multidrop Interface
3.1.1 Ground Lug
The MD485 has a GND lug (see Figure 1). Connect this GND lug to earth
ground with 8 AWG wire. This connection should be as short as possible.
3.1.2 Indicator LEDs
The MD485 has two red LEDs. When 12V power is applied the LEDs light for
one second. The LEDs then begin flashing once every two seconds, while
there is no activity on the ports.
When the RS-485 port is an active port, the LED nearest that connector
(labeled B in Figure 1) indicates traffic on the RS-485 port, and the other LED
(labeled A) indicates traffic on the other active port (CS I/O or RS-232). When
CS I/O and RS-232 are the active ports, the LED between the CS I/O connector
and the RS-232 connector (A) indicates activity on the CS I/O port, and the
other LED (B) indicates traffic on the RS-232 port. When data is being
received and transmitted, the LEDs will flash. The LED for the port that is
transmitting will be on more than the LED for the receiving port.
The LED nearest the RS-485 (B) connector will blink twice a second to
indicate an RS-485 receiving error. This most likely indicates a wiring
problem between the RS-485 ports of the base and remote MD485s.
B
A
GND lug
connects to
earth ground
FIGURE 1. The MD485 has a ground lug that should be attached to
earth ground and LEDs that indicate traffic on the ports.
2