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Solutions to Common Interference Problems in Video Monitoring System


In the process of maintenance of video monitoring system, we often encounter the problem of video screen interference, which makes people headache. Here is a brief introduction of the solution to the common interference problems in video monitoring system.

Striation interference or water ripple interference

1. Check whether the power supply has interference signal superposition, resulting in unclean power supply. This interference can be solved by adding UPS or purifying power supply.

2. The coaxial cable quality problem and poor shielding performance can be solved by replacing the coaxial cable.

3. The interference of strong current interference source to monitoring system can be solved by grounding or adding shielding.

Moire interference

The main cause of Moire interference is the short circuit between the core of the video cable and the screen or the faulty soldering of the BNC head. The video jumper can be replaced or the BNC head can be rewelded.

Vertical bar interference

The main reason for vertical bar interference is that the video line is not 75 ohm, which leads to impedance mismatch. This interference can be realized by "terminal parallel resistance" or "front end series resistance". However, the root cause of this phenomenon is the unqualified quality of wire rod. It is recommended to use national standard pure copper cable.

Snowflake noise interference: the main reason for snowflake noise interference is that the signal attenuation is too large due to the long transmission distance of the coaxial cable. To solve this problem, we can increase a large video anti-jamming device.

To solve the interference:

1. Analyze and find the interference source

We can find the interference source by simple method. The three parts of the interference source are: front end - interference from camera system; middle end - interference from coaxial cable transmission; back end - interference from equipment introduction.

2. Check method of video interference

Put the monitor on the front end to connect with the camera to see if there is interference in the image. If there is interference, solve it from the camera itself (for example, replace the camera). If there is no interference, proceed to the next check.

Disconnect the coaxial cable transmission line from the video distributor or hard disk video recorder in the monitoring room, connect the monitor separately to see if there is interference on the image, and use the anti-jamming device if there is interference. This kind of interference is called "environmental electromagnetic interference", which is relatively common. If there is no interference, it means that the coaxial cable transmission line is not interfered. But once connected with the hard disk video recorder, there will be interference, It shows that the interference caused by the ground potential difference between the system equipment can be solved by adding a photoelectric isolator between the video cable and the hard disk video recorder.

3. Solutions to video interference

Solution to front-end interference: the interference introduced by front-end camera system belongs to equipment interference, which should be solved from the equipment itself (such as camera quality, voltage stability, insulation), and can not be completely solved by using anti-interference device.

Solution of middle end interference: the interference in the transmission part of middle end coaxial cable is the most common, which belongs to "environmental electromagnetic interference". Electromagnetic interference refers to the interference in the surrounding environment of video line, including the interference of variable frequency motor; electromagnetic radiation interference; interference of high-frequency and low-frequency equipment; interference of TV Tower and substation; strong pulse interference caused by high-power electrical appliances such as motor, etc., which can be solved by video anti-interference device.

Solution of back-end interference: the interference between back-end and equipment is mostly caused by the ground potential difference between equipment, resulting in twill and horizontal bar rolling up and down (rolling bar), which can be solved by photoelectric isolator.

4. Interference from power supply

Video interference caused by poor quality power supply is common in front-end interference. In the past, some camera manufacturers chose linear power supply for careful consideration. However, linear power supply has disadvantages such as low conversion efficiency, large volume, high heat generation, high manufacturing cost, etc. nowadays, the stability of switching power supply has been improved a lot, It is recommended to test the power supply as much as possible to check its stability, ripple size and other quality indicators when purchasing the security monitoring power supply for surveillance cameras.