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7
TX
Power terminals are defined as follows:
No.
1
2
3
2.6 External terminal resistance
According to the site situation, the gateway serial port side needs an external 120 Ω
terminal resistance. The RS485 bus supports a maximum of 32 nodes without relay.
The "daisy chain" connection is used between nodes, and terminal resistors are
required at both ends of the communication cable, and their resistance is required to
be approximately equal to the characteristic impedance of the transmission cable. In
short-distance transmission, no terminating resistor is required, that means no
terminating resistor is generally required below 300 meters. The terminating resistor
is connected to the two ends of the transmission cable.
When the gateway is used in the site, if the site RS485 bus is far away and the site
interference is large, so it is necessary to add 120Ω terminal resistance at both ends of
the RS485 bus to prevent the reflection of the serial signal.
Note: 120 Ω resistance attached to the package, please check.
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Symbol
PE
V-
V+
7 / 76
RS232 Sending
Definition
Grounding terminal
Power Input Negative
Power Input Positive
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