June 22, 2023
Top 10 Monitoring Mistakes, Common Error Names, and Common Solutions
1. A large area of deep and chaotic moire noise appears on monitor, as a result of which image is completely destroyed, and image and synchronization signal cannot be formed
The fault is caused by a short circuit or open circuit between live video cable and shield network. This type of failure often occurs on bnc connectors or other types of video connectors. That is, when such a failure phenomenon occurs, often not all signals of entire system have problems, but only appear on those channels with bad connectors. As long as you carefully check these joints one by one, you can solve this problem.
2. Equipment failure caused by incorrect power supply. There are approximately following possibilities of incorrect power supply.
Incorrect power line or supply voltage.
· There is not enough power (or diameter of a certain power line is not enough, voltage drop is too large, etc.).
The transmission line of power supply system has a short circuit, open circuit, instantaneous overvoltage, etc.
Especially due to improper power supply or instantaneous overvoltage, damage to equipment occurs from time to time. Therefore, before putting system into operation and applying power, inspection and inspection must be carried out carefully and strictly, and this should never be taken lightly.
3. A black or white bar appears on monitor screen and slowly scrolls up or down
Reason for failure: determine if it is a power or line problem. Solution: On control host, connect only output of nearest camera without power problems. If above interference phenomenon does not appear on monitor, it means that there is no problem with control host. Next, you can connect a portable monitor to video output of front camera nearby and check each camera in turn.
4. There is no image on monitor
Reason for failure: if power supply is damaged, if camera is damaged, if circuit is broken. Solution: Replace power supply, check if it is ok, if not resolved, check if front camera is ok with engineering insurance, if ok, check if circuit is connected or not.
5. Image switching by host is not clean
The manifestation of this kind of failure is that screen after selection is superimposed by interference of other screens or interference of horizontal sync signal of other images. This is due to poor quality of host or matrix switcher, which cannot meet isolation requirements between images. If an RF transmission system is used, this can also be caused by excessive crosstalk modulation and system intermodulation.
6. PTZ failure
It's common for a stabilizer to fail when it doesn't work properly or at all shortly after use. In addition to product quality factors, this situation is usuallylo, caused by following reasons:
⑴Only allow camera to be mounted on head, which is raised during use. In this case, lifting method increases workload of gimbal, so rotation mechanism of gimbal will be damaged shortly after use, and even motor will burn out.
⑵The combined weight of camera and its protective cover exceeds load-bearing capacity of gimbal. The weight of protective cover is often too large, especially for pan/tilt used outdoors, and there is often a problem that pan/tilt cannot be rotated (especially in vertical direction).
⑶ The external pan/tilt device is malfunctioning or even damaged due to too high or low ambient temperature, poor water and frost protection.
7. Fault phenomenon caused by impedance mismatch of transmission line
The manifestation of this phenomenon is that several vertical stripes are generated on monitor screen at same interval, and frequency of interference signal is basically an integer multiple of line frequency. This is caused by an impedance mismatch caused by impedance of video transmission line not being 75 ohms. It can also be said that this interference phenomenon is caused by characteristic impedance and distribution parameters of video cable not meeting requirements. The solution usually depends on method of "connecting resistance at beginning" or "connecting resistance at end in parallel".
In addition, it is worth noting that at very short video transmission distances (typically within 150 meters), using a video cable with above impedance mismatch and excessive distribution parameters may not necessarily cause aforementioned interference. phenomenon. The main way to solve above problems is to ensure quality when purchasing video cables. If necessary, selective inspection of cables should be carried out.
8. Does image from surveillance camera seem distorted or geometrically distorted?
This phenomenon may be due to a problem with geometry correction circuit of surveillance camera or monitor, or with optical lens, or a poor connection between video connection cable and dome camera. , or characteristic impedance of device differs from output impedance of surveillance camera.
How many black vertical or horizontal bars appear on security camera screen?
In this case, output voltage ripple of machine's power supply is generally too high, and it is necessary to strengthen filter and use a stabilized DC power supply with good performance.
9. Is night vision infrared camera image normal during day but whitish at night?
This phenomenon is usually caused by reflective objects in environment where machine is being used or when it is being used in a nonlarge space due to reflection of infrared light. To solve this problem, you must first determine whether there are reflective objects in use environment, and improve use environment as much as possible. Second, check whether effective infrared distance of machine is consistent with actual use distance; - The remote infrared machine is used in a small space, it will be too strong, causing machine image to be whitish.
10. Common Video Interference Problems
*When a black or white bar appears on monitor screen that scrolls up or down, this is so-called noise at mains frequency of 50 Hz. This type of interference is mainly caused by potential difference loops introduced into system due to improper grounding of external equipment and control center equipment, and can also be caused by deterioration of power supply of equipment itself.
*There is snowflake noise in image, which is mainly caused by signal attenuation in transmission line and superposition of high-frequency noise.
*The video image has ghosting, or image is white, characters are shaky, or several vertical bars appear on monitor screen at same interval. This is because characteristic impedance between video lines or devices is not 75 ohms, resulting in an impedance mismatch.
* Twill interference, beating interference, power interference. When this interference is small, it will not overwhelm a normal image, but when it is large, it will distort image and make it impossible to see. There are many complicated reasons for this, such as quality of video transmission line is not very good, especially bad shielding, or power supply of power system has interference, or there may be a strong source of interference. near system.
*Large area moire, also known as single frequency noise. This phenomenon is mainly due to a malfunction caused by a short circuit or open circuit between live video cable and shield network, or poor contact of BNC connector.