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Connection
4.4 Connecting to the RS485 bus (PAC3120 only)
54
PAC3120 and PAC3220
Equipment Manual, 10/2019,
L1V30425208F-01
Grounding the cable shield
The serial Modbus data line must be shielded. The shield must be connected to protective
ground at one end of the line at least. Strive to achieve grounding of the shield on both sides.
Grounding the common line
The common line must be applied direct to protective ground, preferably at only one point for
the whole bus. It must be ensured that the common signal is routed as a dedicated line.
Polarization
The PAC3120 does not support polarization of the RS485 data lines. Polarization must be
implemented at another point on the bus. The master device usually performs the
polarization.
We recommend polarization with supply of 5 V DC, pull-up resistor with 560
Ω
, pull-down
resistor with 560
Ω
.
Bus terminator
The first and last node in the bus segment must terminate the bus with a terminating resistor.
The PAC3120 does not support bus termination. The bus can be terminated using an
external resistor
≥
120
Ω
. Connect the resistor to terminals
−
/A and +/B of the RS485.
Figure 4-16 Bus termination using external resistor
References
You can find further information in the following specification and the guidelines on the
website of the Modbus Organization (
Содержание SENTRON PAC3120
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Страница 8: ...Table of contents 6 PAC3120 and PAC3220 Equipment Manual 10 2019 L1V30425208F 01 ...
Страница 36: ...Description 2 7 Slots for expansion modules 34 PAC3120 and PAC3220 Equipment Manual 10 2019 L1V30425208F 01 ...
Страница 70: ...Operator control 6 1 Device interface 68 PAC3120 and PAC3220 Equipment Manual 10 2019 L1V30425208F 01 ...
Страница 110: ...Technical data 10 2 Labeling 108 PAC3120 and PAC3220 Equipment Manual 10 2019 L1V30425208F 01 ...
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