SATEC 1771DB - Manual (Page 17)

17
B.2.2 RS-422 Connection with Surge Voltage Protection
TxD
RxD
TxD-
RxD-
TxD
RxD
6
7
RxD'
TxD'
DB9 male connector
2
3
Series PM -280/288/270/290
Powermeters
RxD-
TxD-
RxD
TxD
6
7
DB9 male connector
RxD-
TxD-
RxD
TxD
Series PM-290H Powermeters
Series PM-170 Powermeters
8
9
14
15
16
17
DB25 male connector
1
1
1
GND
GND
GND
* A termination resistor should only be connected at the furthest end of the cable
COM
Z1
Z2 Z3
Z4 Z5
Z6 Z7
Z8
R3
R4
R5
Ω
Z1,Z3,Z5,Z7 - 1N4736A
Z2,Z4,Z6,Z8 - 1N4728A
*R2
R1
R6 **R7
**R8
R1,R2 - 120
R3,R4,R5,R6 - 33
R7,R8 - 1.2 k
Ω
Ω
** In RS-422 communication, a reference or common line should be used in addition to signal lines
use a reference line, place pull-down resistors R7 and R8 on both outputs of the driver to avoid
leaving the line floating when the line is idle
for stable operation. Connect pin 1 of the instruments with pin 7 on the BASIC module. If you don't
1771-DB BASIC module
DB25 male connector
7
4
5
16
14
18
25