After a monitoring system is completed, it needs to enter the commissioning stage and the trial operation stage before it can be delivered. Various failure phenomena may occur, such as common: failure to operate normally, the system fails to meet the design requirements of technical indicators, overall performance and quality Ideal, especially for a complex and large-scale monitoring project, is inevitable, which requires us to do corresponding processing to solve the fault and ensure the normal operation of the system.

1. Equipment failure caused by incorrect power supply. There are roughly the following possibilities for incorrect power supply: incorrect power supply line or power supply voltage, insufficient power (or insufficient wire diameter of a certain power supply line, excessive voltage drop, etc.), short circuit, open circuit, and transient transient in the transmission line of the power supply system Wait. Especially due to power supply error or instantaneous overvoltage, the equipment is damaged. Therefore, in the system debugging, before power supply, must be carefully and strictly checked and checked, and should never be taken lightly.

2. Because there are many connections of some equipment, if the handling is not good, especially the wiring connected to the equipment is not handled well, there will be open circuit, short circuit, poor insulation between wires, wrong wiring, etc., which will cause damage and performance of the equipment. The problem of falling. In this case, you should calmly analyze the fault phenomenon, and determine which lines are connected with problems on a number of lines. Therefore, it is necessary to pay special attention to the connection of the equipment and various lines in this situation should meet the requirements of long-term operation.

3. The quality of the equipment or parts itself. Various equipment and components may have quality problems, which are purely product quality problems, and most of them occur on decoders, electric pan-tilts, transmission components and other equipment. It is worth pointing out that some equipment may not be unusable in terms of quality as a whole, but some technical indicators cannot meet the indicators given in the product manual. Therefore, necessary sampling tests must be carried out on the selected products. If it is a product quality problem, the solution is to replace the product instead of disassembling and repairing by yourself.

4. The problems caused by incorrect connection between equipment (or components) and equipment (or components) will generally occur in the following aspects:

⑴  Impedance does not match.

⑵ The communication interface or communication method does not correspond. This situation mostly occurs between the control host and the decoder or control keyboard and other devices that have a communication control relationship. That is to say, the selected control host and decoder or control keyboard are not caused by the products of the same manufacturer. Therefore, for the host, decoder, control keyboard, etc., products from the same manufacturer should be used.

(3) The drive capacity is insufficient or exceeds the specified number of equipment connections. For example, some screen splitters have an alarm input interface. The product manual shows that the system host connected to the alarm probe, long delay video recorder, etc. is connected to the system. If the alarm probe is connected to the screen splitter, the alarm At the input end, there will be a situation where the alarm signal of the probe must drive the alarm host and the screen splitter.

One of the ways to solve similar problems is to connect the signal of the alarm probe to the screen splitter or video switch host through a dedicated alarm interface box. The second is to design and process signal expansion equipment by yourself when there is no alarm interface box. Or drive equipment.

5. During video transmission, the most common fault phenomenon is that a black bar or white bar appears on the monitor screen, and it scrolls up or down slowly. Therefore, when analyzing such failure phenomena, it is necessary to distinguish two different causes of failure. To distinguish whether it is a power supply problem or a ground loop problem, a simple method is to connect only the output signal of a camera that has no problem with the power supply on the control host. If the above interference phenomenon does not appear on the monitor , Then there is no problem with the control host. Next, a portable monitor can be connected to the video output terminal of the front-end camera and check each camera one by one. If so, proceed with processing. If not, the interference is caused by other reasons such as ground loop.

6. Wood grain-like interference appears on the monitor. The appearance of this kind of interference will not overwhelm the normal image when it is slight, and the image will not be able to be viewed when it is severe (or even break the synchronization). There are many reasons for this failure phenomenon and more complicated. There are roughly the following reasons:

⑴ The quality of the video transmission line is not good, especially the shielding performance is poor (the shielding net is not a good quality copper wire net, or the shielding net is too thin to provide a shielding effect). At the same time, the line resistance of this type of video line is too large, resulting in a large attenuation of the signal, which is also the cause of aggravated failure. In addition, the characteristic impedance of this type of video line is not 75Ω and the parameters exceed the regulations are also one of the reasons for the failure. 

Since the above-mentioned interference phenomenon is not necessarily a fault caused by a poor video cable, the cause of this fault should be judged accurately and cautiously. Only when other possibilities are ruled out can we consider from the perspective of poor video lines. If it is really a cable quality problem, the solution is of course to replace all of these cables and replace them with cables that meet the requirements. This is the solution to the problem completely.

⑵ Caused by the unclean power of the power supply system. The power supply referred to here is not "clean", which means that interference signals are superimposed on the normal power supply (50-cycle sine wave). The interference signals on this kind of power supply mostly come from the equipment using SCRs in the grid. Especially high-current, high-voltage thyristor equipment, pollution to the power grid is very serious, which causes the power supply in the same power grid to be unclean. 

For example, in this power grid, there are high-power SCR frequency regulation devices, SCR rectifier devices, SCR AC/DC converters, etc., which will cause pollution to the power supply. The solution to this situation is relatively simple, as long as the entire system is purified power supply or online UPS power supply, it can basically be solved.

⑶ There are strong sources of interference near the system. This can be judged through investigation and understanding. If this is the reason, the solution is to strengthen the shielding of the camera, and to ground the pipe of the video cable.

7. Faults caused by short circuit or open circuit between the core wire of the video cable and the shielding net. The manifestation of this kind of failure is to produce deeper and more chaotic large-area moire interference on the monitor, so that the image is completely destroyed, and the image and synchronization signal cannot be formed. 

This situation often occurs on BNC connectors or other types of video connectors. That is to say, when this kind of failure phenomenon occurs, it is often not that all the signals of the entire system have problems, but only those that have bad connectors. As long as you carefully check these connectors one by one, you can solve it.

8. Failure phenomenon caused by the characteristic impedance mismatch of the transmission line. The manifestation of this phenomenon is that a number of vertical interferences with equal spacing are generated on the monitor screen. 

The frequency of the interference signal is basically an integer multiple of the horizontal frequency. This is due to the impedance mismatch caused by the characteristic impedance of the video transmission line not 75Ω. It can also be said that this interference phenomenon is caused by the combination of the characteristic impedance and distribution parameters of the video cable that do not meet the requirements. The solution generally depends on the "start-end series connection resistance" or "terminal parallel connection resistance" method to solve the problem. In addition, it is worth noting that when the video transmission distance is very short (usually within 150 meters), the above-mentioned interference phenomenon may not occur when the above-mentioned impedance mismatch and the video cable with excessive distribution parameters are used. The fundamental way to solve the above problems is to ensure the quality when purchasing video cables. The cable should be sampled and tested when necessary.

9. Space radiation interference introduced by the transmission line. This kind of interference phenomenon occurs mostly because there are strong and high-frequency space radiation sources near the transmission system, the front end of the system or the central control room. One solution to this situation is to understand the surrounding environment when the system is established, and try to avoid or stay away from the radiation source; the other is to strengthen the shielding of the front-end and central equipment when the radiation source cannot be avoided. The pipeline of the transmission line uses steel pipe and is well grounded.

10. The malfunction of the gimbal. A gimbal does not work well or cannot rotate at all shortly after use, which is a common malfunction of the gimbal. In addition to product quality factors, this situation is generally caused by the following various reasons:

⑴ Only allow the camera to be installed on the PTZ, when in use, it is hoisted. In this case, the hoisting method causes the operating load of the gimbal to increase, so the rotating mechanism of the gimbal will be damaged soon after use, and the motor may even be burned.

⑵ The total weight of the camera and its protective cover exceeds the load-bearing capacity of the PTZ. Especially for PTZ used outdoors, the weight of the protective cover is often too large, and the problem of the PTZ not moving (especially in the vertical direction) often occurs.

⑶ Outdoor pan/tilt malfunctions or even damages due to high or low ambient temperature, poor waterproof and antifreeze measures.

11. When the distance is too far, the camera (including the lens) and PTZ cannot be remotely controlled through the decoder as a keyboard.

This is mainly because when the distance is too far, the control signal attenuation is too large, and the control signal received by the decoder is too weak. At this time, a relay box should be installed at a certain distance to amplify the shaping control signal.

12. The image contrast of the monitor is too small and the image is light.

If this phenomenon is not the problem of the control host and the monitor itself, it is that the transmission distance is too long or the attenuation of the video transmission line is too large. In this case, a line amplification and compensation device should be added.

13. The image definition is not high, the details are lost, or the color signal is lost or the color saturation is too small when it is serious.

This is because the high-frequency end loss of the image signal is too large, and the signal with the frequency above 3MHz is basically lost. In this case, either because the transmission distance is too long and there is no amplification and compensation device in the middle; or because the distributed capacitance of the video transmission cable is too large; or because there is a concentrated distribution of equivalent capacitance between the core and the shield of the transmission line in the transmission link Caused.

14. Tonal distortion.
This is a failure phenomenon that is prone to occur in the long-distance video baseband transmission mode. The main reason is that the phase shift in the high frequency band of the signal caused by the transmission line is too large. In this case, a phase compensator should be added.

15. The keyboard is malfunctioning.
This phenomenon can be basically determined to be caused by the keyboard "crash" when checking the connection. The keyboard * is used for instructions, generally there are methods to solve the "crash", such as "reset the whole machine", etc., which can be solved by this method. If it cannot be resolved, the keyboard itself may be damaged.

16. The image switching of the host is not clean.

This kind of malfunction is manifested by the interference of other images superimposed on the selected screen, or the interference of the line synchronization signal of other images. This is caused by the poor quality of the host or matrix switch, which cannot meet the requirements for isolation between images. If a radio frequency transmission system is used, it may also be caused by excessive cross-talk modulation and mutual modulation of the system.