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3 RS-485 Cable
3.1 Basic Features
RS-485 industrial buses are half-duplex communication buses whose characteristic impedance is
120Ω. Its maximum load is 32 payloads (including controller devices and controlled devices).
3.2 Common Issues in Use
Users tend to connect devices as the way displayed in Figure 3-1. In this case, the terminal resistance
must be connected to the two devices whose cable length is the longest among all the devices (in
Figure 3-1, cable length between 1# and 15# is the longest). However, this connection manner does
not comply with the RS-485 industrial standard. As a result, common issues like signal reflection and
anti-interference capability reduction will occur. And the Device is out of control or cannot stop.
Figure 3-1 Common method to connect devices
To fix the issues, it is recommended to use RS-485 distributors. The RS-485 distributor can help avoid
the common connection issues so as to improve transmission quality.
