Ideas in Measuring ..
TECHNIQUES LIMITED
Page 8
LDU68 Series Manual
The LDU 68 can also be wired in a 4 wire multi-drop mode where up to 32 devices can be
connected to one bus. To achieve this simply parallel up all connections. So all Rx + terminals are
connected together and are connected to the Tx+ terminal of the host RS485 interface. All Rx -
terminals are connected together and connected to the Tx -terminal of the host RS485 interface. All
Tx + terminals are connected together and are connected to the Rx+ terminal of the host RS485
interface. All Tx- terminals are connected together and connected to the Rx- terminal of the host
RS485 interface. All ground connections are connected together and connected to ground
connection on the host RS485. Terminating resistors (120 Ohms each) should be connected across
each pair of wires both at the host end and on the last device on the bus.
3.4.3 RS485 4 Wire Multi-drop Connections Half Duplex (Recommended)
Gnd
Tx+
Rx+
RS485 Interface
V
cc
Tx-
Rx-
Terminators - 120 Ohm Each
Terminators - 120 Ohm Each
R1
R2
P2
P1
Span Adj.
Made in EU
Zero Adj.
R3
R4
Made in EU
F1
Buss
400mA
R2
P2 Span Adj.
R1
P1
Zero Adj.
R3
R4
Exc
6
7
Gnd
Gnd
Gnd
9
Pwr
Out
In
Out
In
Tx
Tx
Rx
Rx
+
+
0
1
-
-
0
1
8
Sen
5
Inp
4
Inp
3
Sen
2
Exc
1
0
16
17
19
18
15
14
13
12
11
10
+
+
+
-
-
-
I I I
Load Cell Digitising Unit
LDU 68.1
Cert.no. DK0199 - R76 - 10.04
n
max
= 10000
-15°C/+55°C
CE
D
min = 1.0
m
V/VSI
NC
NC
TECHNIQUES LIMITED
www.sensortechniques.com
R1
R2
P2
P1
Span Adj.
Made in EU
Zero Adj.
R3
R4
Made in EU
F1
Buss
400mA
R2
P2 Span Adj.
R1
P1
Zero Adj.
R3
R4
Exc
6
7
Gnd
Gnd
Gnd
9
Pwr
Out
In
Out
In
Tx
Tx
Rx
Rx
+
+
0
1
-
-
0
1
8
Sen
5
Inp
4
Inp
3
Sen
2
Exc
1
0
16
17
19
18
15
14
13
12
11
10
+
+
+
-
-
-
I I I
Load Cell Digitising Unit
LDU 68.1
Cert.no. DK0199 - R76 - 10.04
n
max
= 10000
-15°C/+55°C
CE
D
min = 1.0
m
V/VSI
NC
NC
TECHNIQUES LIMITED
www.sensortechniques.com
Issue 1h
Ideas in Measuring ..
TECHNIQUES LIMITED
Page 9
LDU 68 Series Manual
This page is intentionally left blank
Issue 1h
