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FINGER006 SERIES QUICK INSTALLATION GUIDE
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4.2.2 How to Connect Termination Resistors
Figure: Termination Resistors for 2-Wire RS485 Communication System
Figure: Termination Resistors for 4-Wire RS422 Communication System
4.2.3 Grounding System for Communication Cable
We recommend using proper grounding system on the communication cable. The best method for grounding system is
to put the shield wire of the communication cable to the 1
st
class earth grounding; however it is not so easy to bring the
earth ground to the communication cable and also the installation cost is raised.
There will be three grounding points where you can find during installation;
1)
Earth Ground
2)
Chassis Ground
3)
Power Ground
The most important point for grounding system is not to connect both ends of shield wires to the grounding system; in
this case there will be a current flow through the shield wire when the voltage level of both ends of shield wire is not
equal and this current flow will create noise and interfere to communications.
For the good grounding, we recommend to connecting ONLY one end of shield wire of communication cable to the
grounding system; If you find earth ground nearby, then connect one end of shield wire to earth ground; If you do not
have earth ground nearby, then find chassis ground and connect one end of shield wire to chassis ground; If you do
not find both earth ground and chassis ground, then connect one end of shield wire to power ground. (GND of
FINGER006)
Note that if the chassis ground is not properly connected to the earth and floated from the ground level, then grounding
to the chassis ground will give the worst communication; in this case we recommend to using power ground instead of
chassis ground.
Figure: Grounding System
RS422/RS232
