User Manual

User’s Manual
366
 Mixed ground: The mix ground consists of the feature of the one-point ground and multiple-
point ground. For example, the power in the system needs to use the one-point ground mode
while the radio frequency signal requires the multiple-point ground. So, you can use the following
figure to earth. For the direct current (DC), the capacitance is open circuit and the circuit is one-
point ground. For the radio frequency signal, the capacitance is conducive and the circuit adopts
multiple-point ground.
When connecting devices of huge size (the device physical dimension and connection cable is big
c
omparing with the wave path of existed interference), then there is possibility of interference when
the current goes through the chassis and cable. In this situation, the interference circuit path usually
lies in the system ground circuit.
When considering the earthing, you need to think about two aspects: One is the system compatibility,
and the other is the external interference coupling into the earth circuit, which results in system error.
For the external interference is not regular, it is not easy to resolve.
Appendix 7.3 Thunder Proof Ground Method in the Monitor
System
 The monitor system shall have sound thunder proof earthing to guarantee personnel safety and
device safety.
 The monitor system working ground resistance shall be less than 1Ω.
 The thunder proof ground shall adopt the special ground cable from the monitor control room
to the ground object. The ground cable adopts copper insulation cable or wire and its ground
section shall be more than 20mm
2
.
 The ground cable of the monitor system cannot short circuit or mixed connected with the strong
alternative current cable.
 For all the ground cables from the control room to the monitor system or ground cable of other