(1) After a monitoring system has entered the commissioning phase, commissioning phase, and after delivery, there may be such a failure phenomenon, such as: the technical indicators that cannot be operated normally, the system cannot meet the design requirements, and the overall performance and quality are not satisfactory That is, some "soft problems." These issues are inevitable for a monitoring project, especially for a complex, large-scale monitoring project.
1. Device failure caused by incorrect power supply. Incorrect power supply may be as follows: The power supply line or power supply voltage is incorrect, the power is not enough (or the line diameter of a certain power supply line is not enough, the voltage drop is too large, etc.), the transmission line of the power supply system has a short circuit, open circuit, and instantaneous Pressure and so on. In particular, the device may be damaged due to power supply errors or instantaneous overvoltage. Therefore, in the commissioning of the system, before the power supply, it must be carefully checked and checked carefully and must not be taken lightly.
2. Since there are many links between certain devices (such as cameras with three variable lenses and pan/tilts), if the handling is not good, especially if the lines connected to the device are not handled well, there will be open circuit, short circuit and line. Poor insulation, incorrect wiring, etc. result in equipment damage and performance degradation. In this case, the analysis should be made calmly based on the phenomenon of failure, and it should be determined on which of the lines that the connection is faulty. This will reduce the scope of the problem. It is particularly worth pointing out that cameras with pan-tilt heads have a long time due to all-round movements, resulting in disconnection and breakage of connections that are common. Therefore, special attention should be paid to the connection of equipment and various lines in this case to meet the requirements of long-term operation.
3. The quality of equipment or components itself. In theory, quality problems may occur on various equipment and components. However, from an experience point of view, the pure quality of the product itself occurs in decoders, electric gimbals, and transmission components. It is worth pointing out that the quality of some devices may not appear to be unusable due to their overall quality. However, some technical indicators do not meet the specifications given in the product specifications. Therefore, the necessary sample testing must be performed on the selected product. If it is indeed a product quality problem, the best way is to replace the product and not to dismantle and repair it.
In addition, the most common problems are due to improper adjustment of equipment. For example, the adjustment of the intercept of the camera behind the camera is very detailed and accurate. If the camera is not carefully adjusted, problems such as poor focus or defocusing during the operation of the three variable lenses may occur. In addition, whether the positions of some switches and adjusting knobs on the camera are correct, whether they meet the technical requirements of the system, or the correctness of the encoder coding switch or other adjustable site settings directly affect the normal use of the device itself or affect the normal performance of the entire system. .
4. Problems arising from incorrect connection between equipment (or components) and equipment (or components) will generally occur in the following areas:
(1) Impedance mismatch.
(2) Communication interface or communication method does not correspond. This situation mostly occurs between the control host and a device such as a decoder or a control keyboard that has a communication control relationship. That is, the selected control host and decoder or the control keyboard are not caused by a manufacturer's product. Therefore, the same manufacturer's products should be used for the host, the decoder, and the control keyboard.
(3) The drive capacity is insufficient or exceeds the specified number of device connections. For example, some picture splitters have an alarm input interface and a system host connected to alarm probes, long time delay recorders, etc. is provided in its product specification. If an alarm probe is connected to the screen splitter At the input, the probe's alarm signal will drive both the control panel and the screen divider. In this case, the problem of insufficient driving capacity often arises. The phenomenon is that although the screen divider can alarm, but the input alarm signal is weak and the work is not stable, resulting in the corresponding image of the camera where the alarm signal occurred on the monitor even though the screen instantly converted to a full-screen image However, it is lost (cannot hold), and the image on the monitor is still the multi-image before no alarm.
One of the solutions to the above problem is to use a dedicated alarm interface box to connect the alarm probe signal to the picture splitter or video switching host. Second, when there is no alarm interface box, the signal expansion device can be designed and processed independently. Or drive the device.
The problems mentioned above sometimes also occur in the output and distribution of video signals.
(b) 1. In video transmission, the most common symptom is the appearance of a black bar or white bar on the monitor screen, and it may scroll up or down slowly. Therefore, when analyzing such failure phenomena, two different causes of failures must be distinguished. To distinguish between power supply problems and ground loop problems, an easy way is to connect only one camera power output signal with no power problem to the control host. If the above interference does not occur on the monitor , then there is no problem with the control host. Next, a portable monitor can be connected nearby to the video output of the front camera and each camera can be checked one by one. If yes, handle it. If not, the interference is caused by ground loops and other causes.
2. There is a grainy disturbance on the monitor. The appearance of such interference does not overwhelm the normal image when it is light, and the image cannot be viewed (and even destroys synchronization) when it is severe. The cause of this kind of failure phenomenon is more and more 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 network is not a copper network with good quality, or the shielding network is too thin to be shielded). At the same time, the line resistance of such video lines is too large, which causes the signal to have a large attenuation is also aggravating the cause of the failure. In addition, the characteristic impedance of such a video line is not 75 Ω and one of the causes of the malfunction is that the parameter is out of specification. Since the above-mentioned interference phenomenon is not necessarily a fault caused by a defective video line, the reason for this failure should be accurate and careful when judging. Only from the point of view of the video line can be considered when other possibilities are excluded. If it is really a cable quality problem, the best way is of course to replace all of these cables and replace them with cables that meet the requirements. This is the best way to completely solve the problem.
(2) The power supply system is not "clean". The power source referred to here is not "clean" and means that an interference signal is superimposed on a normal power source (a 50-cycle sine wave). This type of interference signal on the power supply mostly comes from devices that use thyristors in the power grid. In particular, high-current, high-voltage thyristor devices have a very serious pollution to the power grid, which leads to the fact that the power supply in the same power grid is not "clean." For example, in this power grid, there are high-power thyristor frequency modulation speed control devices, thyristor rectifier devices, thyristor AC-DC converter devices, and so on, all of which will cause pollution to 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 through investigation and understanding. If this is the reason, the solution is to strengthen the shielding of the camera, as well as to ground the pipeline of the video cable.
3. The fault caused by the short circuit and open circuit of the core wire of the video cable and the shield network. This failure manifests itself in a deep and chaotic large-area moire on the monitor, so that the image is completely destroyed and the image and synchronization signals cannot be formed. This happens mostly on BNC connectors or other types of video connectors. That is, when this kind of fault phenomenon occurs, it is not always the signal of the entire system that causes problems, but only appears in the number of poorly-connected paths. As long as you carefully check these joints one by one, you can solve.
4. The failure phenomenon due to the mismatch of the characteristic impedance of the transmission line. The manifestation of this phenomenon is that a number of vertical bars of equal spacing are generated on the screen of the monitor, and the frequency of the interference signal is substantially an integral multiple of the line frequency. This is due to impedance mismatch caused by the characteristic impedance of the video transmission line is not 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 do not meet the requirements. The solution is generally to solve the problem by "connecting resistors in series" or "terminating resistors in parallel." In addition, it is worth noting that when the video transmission distance is short (usually within 150 meters), using the above video cable with impedance mismatch and excessive distribution parameters does not necessarily cause the above-mentioned interference phenomenon. The fundamental solution to the above problem is to ensure quality when purchasing video cables. When necessary, the cable should be sampled and tested.
5. Spatial radiation interference introduced by the transmission line. This interference phenomenon is mostly caused by strong, high-frequency spatial radiation sources near the transmission system, the system front-end, or the central control room. One of the solutions to this situation is to understand the surrounding environment when establishing the system and try to avoid or keep away from the radiation source; another way is to strengthen the shielding of the front-end and center equipment when the radiation source cannot be avoided. The pipeline of the transmission line adopts steel pipe and is well grounded.
(c) 1. Failure of the PTZ.
A pan/tilt will not operate quickly or at all after it is used. It is a common fault of the PTZ. The appearance of this situation, apart from the factors of product quality, is generally caused by the following reasons:
(1) Only the pan/tilt head mounted on the camera is allowed to use the hoisting method. In this case, the hoisting method leads to an increase in the operational load of the pan-tilt. Therefore, soon after use, the pan-tilt mechanism will be damaged, and even the motor will be burned.
(2) The total weight of the camera and its protective cover exceeds the weight of the PTZ. Especially for PTZs that are used outdoors, the weight of the protective cover is often too large, and there is often the problem that the PTZ will not move (especially the vertical direction).
(3) The outdoor pan/tilt head is faulty or even damaged due to bad ambient temperature, excessively low temperature, waterproof, and frost protection measures.
2. When the distance is too far, the keyboard (including the lens) and the pan/tilt cannot be remotely controlled by the decoder.
This is mainly because when the distance is too far, the control signal is attenuated too much 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.
3. The image contrast of the monitor is too small and the image is light.
This phenomenon is not the problem of controlling the host computer and the monitor itself, that is, the transmission distance is too long or the attenuation of the video transmission line is too large. In this case, the line amplification and compensation device should be added.
4. The sharpness of the image is not high, the detail is lost, and when the color is serious, color signal loss or color saturation is too small.
This is due to the fact that the loss of the high-frequency end of the image signal is too large, resulting in the basic loss of signals above 3 MHz. This situation may be due to the fact that the transmission distance is too long, and there is no amplification compensation device in the middle; or the distribution capacitance of the video transmission cable is too large; or the equivalent capacitance is concentrated in the transmission link between the core wire and the shielded wire. Caused.
5. Hue distortion.
This is a fault phenomenon that easily occurs in long-distance video baseband transmission. The main reason is caused by the large phase shift of the high frequency band caused by the transmission line. In this case, a phase compensator should be added.
6. * For keyboard failure.
This phenomenon can basically be determined as a keyboard “deadlock†when there is no problem in checking the connection. The instructions for using keyboards are generally used to solve the problem of “crashâ€, such as “resetâ€, etc., which can be solved by this method. If it cannot be solved, it may be that the keyboard itself is damaged.
7. The host does not clean the image.
This failure phenomenon is manifested in the screen after the selection, the interference of other pictures superposed, or the interference of the line synchronization signals of other pictures. This is due to the poor quality of the host or matrix switch and the lack of isolation between images. If a radio frequency transmission system is used, it may also be caused by the system's cross-talk modulation and excessive modulation. A large-scale television monitoring system that operates in conjunction with burglar alarms is a high-tech and complex system. Although various kinds of failure phenomena may occur, as long as the quality of selected equipment and equipment is properly shut down and construction is strictly conducted in accordance with standards and specifications, generally no major problems will arise. Even if it appears, as long as you calmly analyze and think, and don't blindly dismantle, you will solve the problem faster.
1. Device failure caused by incorrect power supply. Incorrect power supply may be as follows: The power supply line or power supply voltage is incorrect, the power is not enough (or the line diameter of a certain power supply line is not enough, the voltage drop is too large, etc.), the transmission line of the power supply system has a short circuit, open circuit, and instantaneous Pressure and so on. In particular, the device may be damaged due to power supply errors or instantaneous overvoltage. Therefore, in the commissioning of the system, before the power supply, it must be carefully checked and checked carefully and must not be taken lightly.
2. Since there are many links between certain devices (such as cameras with three variable lenses and pan/tilts), if the handling is not good, especially if the lines connected to the device are not handled well, there will be open circuit, short circuit and line. Poor insulation, incorrect wiring, etc. result in equipment damage and performance degradation. In this case, the analysis should be made calmly based on the phenomenon of failure, and it should be determined on which of the lines that the connection is faulty. This will reduce the scope of the problem. It is particularly worth pointing out that cameras with pan-tilt heads have a long time due to all-round movements, resulting in disconnection and breakage of connections that are common. Therefore, special attention should be paid to the connection of equipment and various lines in this case to meet the requirements of long-term operation.
3. The quality of equipment or components itself. In theory, quality problems may occur on various equipment and components. However, from an experience point of view, the pure quality of the product itself occurs in decoders, electric gimbals, and transmission components. It is worth pointing out that the quality of some devices may not appear to be unusable due to their overall quality. However, some technical indicators do not meet the specifications given in the product specifications. Therefore, the necessary sample testing must be performed on the selected product. If it is indeed a product quality problem, the best way is to replace the product and not to dismantle and repair it.
In addition, the most common problems are due to improper adjustment of equipment. For example, the adjustment of the intercept of the camera behind the camera is very detailed and accurate. If the camera is not carefully adjusted, problems such as poor focus or defocusing during the operation of the three variable lenses may occur. In addition, whether the positions of some switches and adjusting knobs on the camera are correct, whether they meet the technical requirements of the system, or the correctness of the encoder coding switch or other adjustable site settings directly affect the normal use of the device itself or affect the normal performance of the entire system. .
4. Problems arising from incorrect connection between equipment (or components) and equipment (or components) will generally occur in the following areas:
(1) Impedance mismatch.
(2) Communication interface or communication method does not correspond. This situation mostly occurs between the control host and a device such as a decoder or a control keyboard that has a communication control relationship. That is, the selected control host and decoder or the control keyboard are not caused by a manufacturer's product. Therefore, the same manufacturer's products should be used for the host, the decoder, and the control keyboard.
(3) The drive capacity is insufficient or exceeds the specified number of device connections. For example, some picture splitters have an alarm input interface and a system host connected to alarm probes, long time delay recorders, etc. is provided in its product specification. If an alarm probe is connected to the screen splitter At the input, the probe's alarm signal will drive both the control panel and the screen divider. In this case, the problem of insufficient driving capacity often arises. The phenomenon is that although the screen divider can alarm, but the input alarm signal is weak and the work is not stable, resulting in the corresponding image of the camera where the alarm signal occurred on the monitor even though the screen instantly converted to a full-screen image However, it is lost (cannot hold), and the image on the monitor is still the multi-image before no alarm.
One of the solutions to the above problem is to use a dedicated alarm interface box to connect the alarm probe signal to the picture splitter or video switching host. Second, when there is no alarm interface box, the signal expansion device can be designed and processed independently. Or drive the device.
The problems mentioned above sometimes also occur in the output and distribution of video signals.
(b) 1. In video transmission, the most common symptom is the appearance of a black bar or white bar on the monitor screen, and it may scroll up or down slowly. Therefore, when analyzing such failure phenomena, two different causes of failures must be distinguished. To distinguish between power supply problems and ground loop problems, an easy way is to connect only one camera power output signal with no power problem to the control host. If the above interference does not occur on the monitor , then there is no problem with the control host. Next, a portable monitor can be connected nearby to the video output of the front camera and each camera can be checked one by one. If yes, handle it. If not, the interference is caused by ground loops and other causes.
2. There is a grainy disturbance on the monitor. The appearance of such interference does not overwhelm the normal image when it is light, and the image cannot be viewed (and even destroys synchronization) when it is severe. The cause of this kind of failure phenomenon is more and more 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 network is not a copper network with good quality, or the shielding network is too thin to be shielded). At the same time, the line resistance of such video lines is too large, which causes the signal to have a large attenuation is also aggravating the cause of the failure. In addition, the characteristic impedance of such a video line is not 75 Ω and one of the causes of the malfunction is that the parameter is out of specification. Since the above-mentioned interference phenomenon is not necessarily a fault caused by a defective video line, the reason for this failure should be accurate and careful when judging. Only from the point of view of the video line can be considered when other possibilities are excluded. If it is really a cable quality problem, the best way is of course to replace all of these cables and replace them with cables that meet the requirements. This is the best way to completely solve the problem.
(2) The power supply system is not "clean". The power source referred to here is not "clean" and means that an interference signal is superimposed on a normal power source (a 50-cycle sine wave). This type of interference signal on the power supply mostly comes from devices that use thyristors in the power grid. In particular, high-current, high-voltage thyristor devices have a very serious pollution to the power grid, which leads to the fact that the power supply in the same power grid is not "clean." For example, in this power grid, there are high-power thyristor frequency modulation speed control devices, thyristor rectifier devices, thyristor AC-DC converter devices, and so on, all of which will cause pollution to 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 through investigation and understanding. If this is the reason, the solution is to strengthen the shielding of the camera, as well as to ground the pipeline of the video cable.
3. The fault caused by the short circuit and open circuit of the core wire of the video cable and the shield network. This failure manifests itself in a deep and chaotic large-area moire on the monitor, so that the image is completely destroyed and the image and synchronization signals cannot be formed. This happens mostly on BNC connectors or other types of video connectors. That is, when this kind of fault phenomenon occurs, it is not always the signal of the entire system that causes problems, but only appears in the number of poorly-connected paths. As long as you carefully check these joints one by one, you can solve.
4. The failure phenomenon due to the mismatch of the characteristic impedance of the transmission line. The manifestation of this phenomenon is that a number of vertical bars of equal spacing are generated on the screen of the monitor, and the frequency of the interference signal is substantially an integral multiple of the line frequency. This is due to impedance mismatch caused by the characteristic impedance of the video transmission line is not 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 do not meet the requirements. The solution is generally to solve the problem by "connecting resistors in series" or "terminating resistors in parallel." In addition, it is worth noting that when the video transmission distance is short (usually within 150 meters), using the above video cable with impedance mismatch and excessive distribution parameters does not necessarily cause the above-mentioned interference phenomenon. The fundamental solution to the above problem is to ensure quality when purchasing video cables. When necessary, the cable should be sampled and tested.
5. Spatial radiation interference introduced by the transmission line. This interference phenomenon is mostly caused by strong, high-frequency spatial radiation sources near the transmission system, the system front-end, or the central control room. One of the solutions to this situation is to understand the surrounding environment when establishing the system and try to avoid or keep away from the radiation source; another way is to strengthen the shielding of the front-end and center equipment when the radiation source cannot be avoided. The pipeline of the transmission line adopts steel pipe and is well grounded.
(c) 1. Failure of the PTZ.
A pan/tilt will not operate quickly or at all after it is used. It is a common fault of the PTZ. The appearance of this situation, apart from the factors of product quality, is generally caused by the following reasons:
(1) Only the pan/tilt head mounted on the camera is allowed to use the hoisting method. In this case, the hoisting method leads to an increase in the operational load of the pan-tilt. Therefore, soon after use, the pan-tilt mechanism will be damaged, and even the motor will be burned.
(2) The total weight of the camera and its protective cover exceeds the weight of the PTZ. Especially for PTZs that are used outdoors, the weight of the protective cover is often too large, and there is often the problem that the PTZ will not move (especially the vertical direction).
(3) The outdoor pan/tilt head is faulty or even damaged due to bad ambient temperature, excessively low temperature, waterproof, and frost protection measures.
2. When the distance is too far, the keyboard (including the lens) and the pan/tilt cannot be remotely controlled by the decoder.
This is mainly because when the distance is too far, the control signal is attenuated too much 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.
3. The image contrast of the monitor is too small and the image is light.
This phenomenon is not the problem of controlling the host computer and the monitor itself, that is, the transmission distance is too long or the attenuation of the video transmission line is too large. In this case, the line amplification and compensation device should be added.
4. The sharpness of the image is not high, the detail is lost, and when the color is serious, color signal loss or color saturation is too small.
This is due to the fact that the loss of the high-frequency end of the image signal is too large, resulting in the basic loss of signals above 3 MHz. This situation may be due to the fact that the transmission distance is too long, and there is no amplification compensation device in the middle; or the distribution capacitance of the video transmission cable is too large; or the equivalent capacitance is concentrated in the transmission link between the core wire and the shielded wire. Caused.
5. Hue distortion.
This is a fault phenomenon that easily occurs in long-distance video baseband transmission. The main reason is caused by the large phase shift of the high frequency band caused by the transmission line. In this case, a phase compensator should be added.
6. * For keyboard failure.
This phenomenon can basically be determined as a keyboard “deadlock†when there is no problem in checking the connection. The instructions for using keyboards are generally used to solve the problem of “crashâ€, such as “resetâ€, etc., which can be solved by this method. If it cannot be solved, it may be that the keyboard itself is damaged.
7. The host does not clean the image.
This failure phenomenon is manifested in the screen after the selection, the interference of other pictures superposed, or the interference of the line synchronization signals of other pictures. This is due to the poor quality of the host or matrix switch and the lack of isolation between images. If a radio frequency transmission system is used, it may also be caused by the system's cross-talk modulation and excessive modulation. A large-scale television monitoring system that operates in conjunction with burglar alarms is a high-tech and complex system. Although various kinds of failure phenomena may occur, as long as the quality of selected equipment and equipment is properly shut down and construction is strictly conducted in accordance with standards and specifications, generally no major problems will arise. Even if it appears, as long as you calmly analyze and think, and don't blindly dismantle, you will solve the problem faster.
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