Application of weighted anti-jamming device in high-rise elevator video transmission

Anti-jamming problem of high-level elevator video transmission in Shanghai

About the anti-interference problem of high-end elevator video transmission in Shanghai, the situation introduced by Shanghai friends is roughly as follows: the old elevator uses a common motor, the interference frequency is very low, and the anti-interference problem is better solved. Most of them now use variable frequency power motors, which have high interference The harmonics are very "rich", the frequency spectrum is very wide, and the high-frequency interference is very serious; especially in Shanghai's high-rise communities, office buildings, and floors are too high, the elevator video cable has already taken measures to enter the elevator shaft from the "middle" It is necessary to wear metal pipes and go through metal wire ducts. Special elevator cables are also used. Some also use "advanced imported elevator cables", but the accompanying cables are still very long. The interference has always been a headache: They tested all the anti-interference products that were available. Although most of them had a certain effect, the results were always unsatisfactory: there was residual interference, especially residual high-frequency interference, and the image was not satisfactory. Some "brightness blossoms" are distorted, and the characters displayed on the floor are deformed, affecting synchronization and so on.

About the basic principle of weighted anti-jamming device

The basic principle of the weighted anti-jamming device is to amplify the video signal to improve the signal / interference ratio. This is a very primitive and basic principle. EIE weighted anti-jamming device integrates and creatively develops EIE's original "weighted video amplification" patent technology, forming a practical function with higher frequency and stronger anti-interference ability. This is a new product containing two patented technologies. It also has the dual functions of anti-interference and compensation of cable transmission attenuation distortion (video recovery). What the product pursues and realizes is the video transmission channel technical standard, whether it is used for low-resolution video transmission of video doorbells or 480-line high-resolution video transmission, it can be transmitted with high fidelity. If the transmission equipment transmits 480 lines of high-resolution video signals into 420 lines, although the subjective feeling is "the image is okay", as a video transmission channel device, this is a 100% unqualified product. The weighted anti-jamming device of the eie brand belongs to the original video signal transmission equipment, and there is no process of modulation conversion, so there is no trouble and problem caused by these processes.

Weighted anti-jamming device challenges Shanghai high-rise elevator frequency converter interference

The weighted anti-jamming device has been on the market since January 2005. Among the more than 300 engineering application examples before the Shanghai exhibition in late May, there were more than 30 elevator anti-jamming application examples, but the high-level elevators are still few. At the Shanghai exhibition on May 25-28, Yantai EIE conducted the first public demonstration of video transmission interference and anti-interference. Demonstrates eight types of interference such as wood grain interference, diagonal vertical interference, wire drawing interference, radio grid interference, 50 Hz power interference, 100 Hz power interference, white noise broadband interference, pulse noise interference, etc. Interference effect demonstration More people are interested in application connection and usage.

Because the weighted anti-jamming device is small, the installation is simple and convenient, and the exhibition is very busy, I invite some friends in Shanghai to take the product and go to the high-level elevator project for field testing. The feedback information is the same-the interference is resolved very well, there is no residual interference, and the image quality is obviously superior. There is a case where the anti-interference effect, image quality and floor character display quality are all satisfactory under the elevator running state, that is, the transient image jump and black screen problem occur when the elevator door is opened and closed. The reason is to be investigated.

Why some anti-interference effects are not obvious

To solve the video interference in the project, we should first calmly analyze and judge the main part of the interference source. The three major sources of interference are: interference introduced by the front-end camera system, interference introduced by the transmission cable, and interference introduced by the back-end equipment. The interference introduced by the front-end and back-end equipment belongs to equipment interference, which should be solved from the equipment itself, and cannot be solved by the jammer; the weighted anti-jamming device is suitable for solving the interference introduced by the transmission cable. For example, there is a project where several channels have interference, and most of the problems are solved well with weighted anti-jamming devices, but there is one channel with anti-jamming effects that are not obvious, and the results of replacing anti-jamming devices are all the same. Finally, the cause was the power adapter problem of the front camera. Let's look at an example of Jinan: using the monitor alone, the image has no interference, and there is interference when connected to the hard disk. The effect of using a weighted anti-interference device is not obvious. After consultation through telephone consultation, it was initially judged that the interference came from the back-end equipment. After careful inspection by the engineering staff, it was the air conditioner and the monitoring equipment that were shared on the same wire. After the air conditioner was changed to the line, the interference was eliminated. From more than 300 engineering application examples, the return of weighted anti-jamming devices is 4-5%; of which, the product failure is less than 2%, and the rest of the returned products are fully normal after the return test. The reason for the return is "anti-interference effect" Not obvious ". According to the investigation and analysis of the EIE laboratory, the reason is that the interference part is judged incorrectly.

Eliminate interference with experience exchange

If after using the weighted anti-jamming device, it is found that the anti-jamming effect is not obvious, you can use the following steps to check: first use the monitor to check the camera output image at the front end of the transmission cable, and observe with a small DC monitor to avoid the influence of AC circuit interference Hard disk recorder image inspection is not easy to distinguish the interference parts, if there is interference, check the camera power supply; the quality of the indirect points in the cables, cable heads and cables of the transmission line can be accurately judged by the weighted anti-jamming device "effective, invalid"; finally the back-end equipment Check (distributor, splitter, matrix, DVR and other related connected equipment). The problem of interference caused by most equipment is relatively easy to investigate. The more difficult and difficult to think of is "underground handshake interference", which is the mutual interference introduced by the ground wire between the equipment; pay special attention to the "ground" in the power cord and the power socket. "Wire processing, more examples are to remove the" ground "of the three plugs into two plugs. It is recommended that engineering design and construction personnel pay attention to study and check the "grounding, repeated grounding, working grounding, protective grounding, overvoltage protection grounding, neutral point direct grounding, neutral point indirect grounding" in the building and the main control equipment power supply system. , Zero connection, zero connection protection, etc., the actual power supply system is grounded in a variety of ways, and this aspect still needs to continue to accumulate and exchange engineering experience.

The methods for solving the interference in different parts are different. Only the interference in the middle transmission part belongs to the common "environmental electromagnetic interference", and it is generally effective to solve with various types of video anti-jamming devices. When choosing products, should pay attention to whether the anti-interference bandwidth is enough? What is the degree of residual interference (interference suppression capability)? Is it capable of transmission compensation (attenuation and distortion)? The result of the weighted anti-jamming device for front-end and back-end equipment interference is "ineffective or insignificant". There are two types of such interference. The first is equipment failures and problems, including camera problems, power supply problems, voltage reduction problems, back-end equipment, power supply, and board problems, etc. The solution is to find and eliminate equipment failures; The two types of equipment interference are conducted interference, including the interference between the monitoring equipment through the connection of the wiring and the power line, and the interference introduced by the monitoring equipment through the power supply system and the grounding system. Eliminating such interference is difficult, and the It's because "unexpected".