3 RS-485 Cable
3.1 Basic Features
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TRS-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).
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.
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
