IDTECK GE313, Руководство по эксплуатации

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4.2.2 HOW TO CONNECT TERMINATION RESISTORS
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Figure: Termination resistors for 2 wire RS485 communication system
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4.2.3 GROUND SYSTEM
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We recommend to using proper grounding system of the communication cable. The best method for grounding
system is to put the shield wire of the communication cable to the 1
P
st
P
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 point 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 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
GE313) 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