2) Rs485 Connection Not Shielded; 3) Rs485 Connection Shielded - ABB ANR96 User Manual

ANR96 - USER MANUAL
8.4.2) RS485 CONNECTION NOT SHIELDED
Once a RS485 network has been configured; to communicate between the Host (computer) and the
instrument(s) (ANR) a serial interface converter must be wired between PC and instrument(s) as
mentioned on the above picture.
In serial line over 500 mt, connect a line termination resistor (Rt=100Ω - 120Ω) between the two
twisted pair cables leading from the converter at the end of the network (last connected instrument).
It's recommended to use always twisted pair cable with minimum cross-section of 0.36mm
and capacity less than 60 pF/m.
8.4.3) RS485 CONNECTION SHIELDED
Although the signal is given by the difference between A and B voltage, a ground connection is
needed to eliminate or to reduce the common mode noise induced (into the bus).
To reduce the EMI interferences need to connect the shield directly to a ground at one end and with a
series RC network at the other end.
R = 100Ω C = 33µF.
The max length of the stubs is 20cm.
RS232/RS485
Max 32 ANR; max 1200 mt
converter
CE
B
RS232/RS485
converter
A
RS232
Do2-
L1V
Do2+
L2V
L3V
N
S1 S2 S1 S2 S1 S2 L N
I1 I2 I3 Vaux
Max 32
Do2-
L1V
Do2+
L2V
L3V
N
L N
CE S1 S2 S1 S2 S1 S2
I1 I2 I3 Vaux
-27-
Do2-
L1V
Do2+
L2V
L3V
N
S1 S2 S1 S2 S1 S2 L N
CE
I1 I2 I3 Vaux
ANR
; max 1200 mt
Do2-
L1V
Do2+
L2V
L3V
N
L N
CE S1 S2 S1 S2 S1 S2
I1 I2 I3 Vaux
2
(22AWG)
Rt