Delta Embedded DVR User Manual download pdf (Page 160)

160

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 comparing with the wave path of existed interference), then there are 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: The first 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.

3. Thunder proof ground method in the monitor system

z The monitor system shall have sound thunder proof earthing to guarantee personnel safety

and device safety.

z The monitor system working ground resistance shall be less than 1Ω.

z 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 20mm2.

z The ground cable of the monitor system can not short circuit or mixed connected with the

strong alternative current cable.

z For all the ground cables from the control room to the monitor system or ground cable of

other monitor devices, please use the copper resistance soft cable and its section shall be

more than 4mm2.

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Delta Embedded DVR User Manual Page 160