What are the common faults in the monitoring system?

What are the common faults in the monitoring system?

(one)

After a monitoring system enters the commissioning phase, the commissioning phase, and after delivery, it is very likely that such a failure phenomenon occurs, such as: failure to operate normally, the system does not meet the technical requirements of the design requirements, the overall performance and quality are not ideal, That is, some "soft problems." These problems are inevitable for a monitoring project, especially for a complex, large-scale monitoring project.

1. Equipment failure caused by incorrect power supply.

The power supply is incorrect. There are several possibilities: the power supply line or the power supply voltage is incorrect, the power is not enough (or the wire diameter of a certain power supply line is not enough, the voltage drop is too large, etc.), and the transmission line of the power supply system is short-circuited, open, and instantaneous. Pressure and so on. In particular, equipment damage due to power supply errors or transient overvoltages may occur. Therefore, in the system debugging, before power supply, we must carefully check and check carefully, and should not be taken lightly.

2. Because some devices (such as cameras with three variable lenses and pan/tilt) have many links, if the processing is not good, especially if the line connected to the device is not handled well, there will be open circuit, short circuit, and line. Poor insulation, mis-wiring, etc. cause damage to equipment and performance degradation. In this case, the analysis should be carried out in a calm manner based on the fault phenomenon, and it is judged that the fault phenomenon occurs on the lines due to the problems of the connection of the lines. This will narrow the scope of the problem. It is particularly worth noting that the camera with the pan/tilt is very common due to the all-round movement, which leads to the disconnection and breakage of the connection. Therefore, the connection between the equipment and various lines that pay special attention to this situation should meet the requirements for long-term operation.

2. Quality problems with the equipment or components themselves.

In theory, quality problems can occur with various equipment and components. However, from the experience point of view, the quality problems of the products themselves are mostly on the decoder, electric cloud platform, transmission components and other equipment. It is worth pointing out that some equipments may not have the problem of being unusable in quality as a whole, but from some technical indicators, they fail to reach the indicators given in the product manual. Therefore, the necessary sampling tests must be performed on the selected products. If it is a product quality problem, the best way is to replace the product, and not to disassemble and repair it.

In addition to this, the most common problem is due to improper adjustment of the device. For example, the adjustment of the focal length after the camera is installed is very detailed and accurate work. If not carefully adjusted, there will be problems such as poor focusing or defocusing during various operations of the three variable lenses. In addition, whether the position of some switches and adjustment knobs on the camera is correct, whether it meets the technical requirements of the system, whether the decoder code switch or other adjustable parts are set correctly will directly affect the normal use of the device itself or affect the normal performance of the entire system. .

4. The problem of incorrect connection between the device (or component) and the device (or component) will generally occur in the following aspects:

(1) Impedance mismatch.

(2) The communication interface or communication method does not correspond. This situation mostly occurs between the control host and the device with communication control relationship such as the decoder or the control keyboard. That is to say, the selected control host and the decoder or the control keyboard are not caused by a manufacturer's product. Therefore, for the host, decoder, control keyboard, etc. should use the same manufacturer's products.

(3) The drive capacity is insufficient or exceeds the specified number of device connections. For example, some picture splitters with alarm input interface in their product manuals are given to the system host connected to the alarm probe, long delay video recorder, etc., if the alarm probe is connected to the screen splitter alarm At the input end, the alarm signal of the probe will be driven to both the control panel and the screen splitter. In this case, there is often a problem of insufficient driving ability. The phenomenon is that although the picture splitter can alarm, but the input alarm signal is weak and the operation is unstable, so that the image picture of the camera corresponding to the alarm signal is instantaneously converted into a full screen picture on the monitor. But it is lost (can't hold), and the image on the monitor is still multi-screen before the alarm.

One of the methods to solve the above problems is to connect the signal of the alarm probe to the picture splitter or the video switching host through a dedicated alarm interface box, and the second is to design the processing signal expansion device without the alarm interface box. Or drive the device.

The problems mentioned above may sometimes appear in the output and distribution of video signals.

(two)

1. In video transmission, the most common symptom phenomenon is that a black bar or white bar appears on the monitor's screen, and slowly scrolls up or down. Therefore, when analyzing such fault phenomena, it is necessary to distinguish between two different causes of faults. To distinguish between the problem of the power supply or the problem of the ground loop, an easy way is to connect only one camera with a power supply without a problem on the control panel. If there is no such interference on the monitor. , then the control host has no problem. Next, use a portable monitor to connect to the video output of the front camera and check each camera one by one. If so, proceed with the processing. If not, the interference is caused by other reasons such as the ground loop.

2. Wood grained interference appears on the monitor. The appearance of such interference does not overwhelm the normal image when it is slight, and the image cannot be viewed (or even destroys the synchronization) when it is severe. The causes of such failures are more complicated and complicated. There are roughly the following reasons:

(1) 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 mesh, or the shielding mesh is too thin to prevent shielding). At the same time, the line resistance of such video lines is too large, which causes a large attenuation of the signal, which is also a cause of aggravation. In addition, the characteristic impedance of such video lines is not 75Ω and the parameter is out of specification is also one of the causes of failure. Since the above-mentioned interference phenomenon is not necessarily a failure caused by a bad video line, the cause of such a failure is accurate and prudent in judging. Only when the other possibilities are excluded can we consider from the perspective of the video line. If it is really a cable quality problem, the best way is to replace all of this cable and replace it with a cable that meets the requirements. This is the best way to solve the problem completely.

(2) Due to the fact that the power supply of the power supply system is not "clean". The power source referred to here is not "clean", which means that an interference signal is superimposed on a normal power source (a 50-sine sine wave). The interference signals on such power sources are mostly from devices using thyristors in the power grid. Especially for high-current, high-voltage thyristor equipment, the pollution of the power grid is very serious, which leads to the power supply in the same power grid is not "clean." For example, there are high-power thyristor frequency modulation speed regulation devices, thyristor rectifier devices, thyristor AC/DC converters, etc. in the power grid, which will pollute the power supply. The solution to this situation is relatively simple, as long as the entire system is powered by a clean power supply or an online UPS.

(3) There is a strong source of interference near the system. This can be judged by investigation and understanding. If this is the case, the solution is to strengthen the shielding of the camera and ground the pipeline of the video cable.

3. Failure due to short circuit and open circuit of the core wire of the video cable and the shielded cable. This type of failure is manifested by the generation of deeper and more chaotic large-area moire on the monitor, so that the image is completely destroyed, and the image and synchronization signals are not formed. This is often the case with BNC connectors or other types of video connectors. That is to say, when such a fault phenomenon occurs, it is often not a problem of the signals of the entire system, but only the number of paths in which the joints are not good. As long as you carefully check these connectors one by one, you can solve them.

4. A fault phenomenon caused by a mismatch in the characteristic impedance of the transmission line. This phenomenon is manifested in that a plurality of vertical strips of equal spacing are generated on the screen of the monitor, and the frequency of the interference signal is substantially an integer multiple of the horizontal frequency. This is due to the impedance mismatch caused by the characteristic impedance of the video transmission line being 75Ω. It can also be said that this interference phenomenon is caused by the fact that the characteristic impedance and distribution parameters of the video cable are not in compliance with the requirements. The solution is generally solved by the method of “starting series resistor” or “terminal paralleling resistor”. In addition, it is worth noting that when the video transmission distance is short (usually within 150 meters), the above-mentioned interference phenomenon may not occur with the video cable having the above-mentioned impedance mismatch and excessive distribution parameters. The fundamental solution to the above problem is to ensure quality when purchasing video cables. The cable should be sampled if necessary.

5. Space radiation interference introduced by the transmission line. Most of this interference phenomenon occurs because there is a strong, high-frequency spatial radiation source 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, try to avoid or keep away from the radiation source; another method is to strengthen the shielding of the front end and the center equipment when the radiation source cannot be avoided. The pipeline of the transmission line is made of steel pipe and well grounded.

(three)

1. The failure of the gimbal.

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

(1) Only the gimbal that is installed in the camera is allowed to be hoisted during use. In this case, the hoisting method leads to an increase in the operating load of the gimbal, so that the use of the gimbal's rotating mechanism may be damaged or even burned out.

(2) The total weight of the camera and its protective cover exceeds the weight of the gimbal. Especially for the outdoor use of the gimbal, the weight of the protective cover is often too large, and the problem that the gimbal can not turn (especially in the vertical direction) often occurs.

(3) The outdoor cloud platform is faulty or even damaged due to excessive ambient temperature, low temperature, poor waterproofing and antifreeze measures.

2. When the distance is too far, the operation keyboard cannot remotely control the camera (including the lens) and the pan/tilt through the decoder.