Elevator video interference solution_Anhui Honglin Instrument Cable Co., Ltd.

Elevator video interference solution

Author：hlyb Add Time：2016-04-29 11:09:10

In the TV monitoring project, it is a common problem that the camera inside the elevator is disturbed, and it is also one of the problems that the engineer * * * is difficult to solve. This paper analyzes the causes of elevator video interference, and discusses the avoidance and solutions, hoping to be helpful to you. 1、 Cable selection in elevator monitoring. In elevator monitoring, because the elevator is moving, it is different in wiring

1、 Cable selection in ladder monitoring

In elevator monitoring, because the elevator is moving, the wiring is different from the pipe (slot) wiring mode of fixed point monitoring. In the selection of cable, it also requires high mechanical strength. Often, engineers pay attention to the mechanical strength of cable in wiring and ignore its video transmission characteristics.

Because the elevator room is a close and narrow space, and there are many other control, lighting, fan and other cables in the elevator, it is also very difficult for the wiring of video cables. Therefore, the following principles should be followed in the selection of cables.

1. Meet the tensile strength: half of the elevator cables are used for extension. The high-rise elevator * * * can reach more than 1000 meters, and the self weight of the cable of more than 1000 meters is nearly 100 kg, so the cable must have sufficient tensile strength. Now there is a special cable for self-supporting flat composite elevator in the market. This cable combines the video cable, power line, data line and steel strand to make a flat ribbon cable. In this way, the tension of the whole cable is borne by the steel strand, and the tensile strength is greatly improved, so that the cable will not be broken during the operation of the elevator.

2. Good electrical parameters: as the cable runs up and down in the elevator, there is always a section in the middle of the cable that will bend and deform under the action of gravity, which will cause changes in the impedance characteristics of the cable. The deformation coefficient of the cable with poor quality is large after stress. After impedance mismatch, the visual frequency attenuation is naturally large, the video signal-to-noise ratio is reduced, and the image is easy to be disturbed.

3. In the selection of cables, try to choose well shielded and thick wire diameter, so as to prevent the "invasion" of interference signals.

2、 Cable wiring skills in elevator monitoring

In the elevator monitoring wiring, the method of bundling together with other cables is often adopted. Since the AC signals in other cables leak outward through the transmission cable, and the video cable is tied parallel to it for a long distance, it is equivalent to a pair of "antenna", which will couple the interference signals. Therefore, the bundling length parallel with other cables shall be shortened as far as possible in the wiring. If possible, The video cable can be fixed at the middle point of the elevator shaft and led back to the main control room from other channels (cable shaft), which can avoid cable coupling interference and ensure the freedom of the cable. For conditional projects, the control line and lighting cable used by the elevator can be shielded to reduce external radiation and avoid video interference.

3、 Causes of common interference

1. At present, AC variable frequency speed regulation technology is basically used in elevators, and the variable frequency governor itself has strong high-frequency parasitic interference. According to the measured results, since the video signal is 0-6 MHz signal, and the bandwidth radiated by the variable frequency governor is 0-10 MHz, the amplitude of the interference signal is very strong, This interference signal can enter the video monitoring system through the power line and space radiation to interfere with the video image. This interference source is the main reason why elevator video monitoring is vulnerable to interference, and it is also an interference problem that * * * can not solve.

2. Since the power supply used for the elevator camera is taken from the 380V power supply of the elevator, and the elevator adopts a variable frequency motor, it has an impact on the camera and transmission line;

3. Controller interference: the control part in the elevator (including up and down door opening and closing) is a controller of about 11 megabytes. Once started, it will constantly send control signals and 11 megabytes of control waves, which will interfere with the video accompanying cable; (this is the reason for the increased interference caused by driving the elevator)

4. In elevator monitoring, the camera power supply * * * is good. It is centralized DC power supply from the main control room. If it is unable to supply power directly, choose to take power from the lighting power in the elevator car. However, at present, the lighting in the elevator of most elevator manufacturers is fluorescent lighting, and this kind of lamps use electronic ballasts. When the electronic ballasts work, they will also produce strong AC parasitic interference output.

4、 Avoidance of elevator interference

The main causes of elevator video interference have been analyzed in detail. As long as the causes of interference are identified, the interference problem can be solved. To solve the elevator interference, we should mainly start from the following points.

1. Select the video cable with small attenuation coefficient, good shielding performance and high tensile strength, which can improve its anti-interference ability and reduce video attenuation.

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Elevator video interference solution