[ Huaqiang Security Network News
In the design of TV monitoring system, the equipment selection problem of TV monitoring system is often involved. More prominent is the combination of front-end camera and terminal display. Therefore, we often choose TV monitoring system equipment when we can not match, and strictly select according to the monitored environment.
General selection principle
Styling products that comply with current national and industry standards should be used.
All equipment in the system must be produced by the manufacturer holding the production license. The equipment should have the manufacturer's nameplate or trademark, inspection certificate and instructions for use.
For non-shaped auxiliary equipment or ancillary equipment, it must meet the quality requirements of engineering design.
For domestic products and foreign products with similar price and performance indicators, domestic products should be given priority to protect the development of national industries.
The performance and technical requirements of all equipment in the system should be consistent and meet the system design requirements.
The system's TV system should be the same as the current standard of China's radio and television.
The video input and output impedance of the system and the impedance of the cable should be 75Î©, and the input and output impedance of the audio equipment should be high impedance or 600Î©.
Next, we will focus on the selection principle of the front-end camera part and terminal monitor.
Principles for selecting equipment for camera equipment
Cameras with different sensitivities should be selected based on the illuminance of the monitored target. The minimum ambient illumination of the surveillance target should be 10 times higher than the minimum illumination of the camera.
The choice of camera lens should meet the following requirements:
1 The focal length of the lens should be determined according to the size of the field of view and the distance between the lens and the monitoring target, and calculated according to the formula (1-31).
When the fixed monitoring target is ingested, a fixed focal length lens can be selected; when the viewing distance is small and the viewing angle is large, a wide-angle lens can be selected; when the viewing distance is large, a telescope head can be selected; when it is necessary to change the viewing angle or the viewing angle range of the monitoring target When larger, a zoom lens should be used.
2 When the monitoring target illumination changes, the aperture adjustable lens should be used.
3 When remote control is required, a remote lens unit with light focus, aperture opening, and zoom can be selected.
According to the working environment, the corresponding camera protection cover should be selected. The protective cover can be equipped with a temperature control system and a remote control wiper as needed.
A camera bracket or a pan/tilt can be used to fix the camera's support on a specific location. When a camera needs to monitor multiple scenes in different directions, it should be equipped with an auto-focusing device and a remote-controlled electric pan/tilt.
The resolution of a typical color CCD camera is lower than that of a black and white CCD camera, and the commercial price is more than doubled. Therefore, if the target being observed does not have obvious color marks and differences, it is an image close to the contrast of black and white contrast, and it is desirable to use a black and white camera to clearly reflect the details of the situation being monitored. If macroscopic monitoring is carried out, the color of the scene being monitored is richer. The contrast of the image obtained by the color camera is more vivid and full of three-dimensionality, and the degree of clarity of the visual inspection is higher than that of black and white. If you want to not only be clear about the details of the image being monitored, but also be able to faithfully reproduce the color of the target, you should use a high-end color CCD camera.
When the camera needs to be concealed, it can be placed in the ceiling or wall, and the lens can be a pinhole or a prism lens. For the anti-theft system, an additional external sensor and system combination can be installed to perform linkage alarm.
System equipment for monitoring underwater targets should use high-sensitivity cameras and sealed pressure and water resistant protective covers, as well as water seepage alarms.
Water-cooled or air-cooled protective covers shall be used for equipment that monitors special high-temperature conditions such as steel smelting. When using an air-cooled hood, it is particularly important to point out that the air inlet must be equipped with an effective oil-water filter. Otherwise, the camera lens will soon be contaminated by oil and water, resulting in a sharp drop in sharpness and even damage to the machine. When using a wind or water-cooled cover, it is best to install an over-temperature alarm and an automatic power-off controller to avoid burning the camera due to a malfunction of the cooling system.
When the ordinary camera is used at night, to ensure sufficient illumination, an automatic iris lens should be used, and an auto focus function is more desirable.
The low-light camera should be used with an infrared light source that is compatible with the field of view.
The indoor camera can usually be equipped with a fixed focal length lens, and if necessary, a cloud platform and a protective cover can be added.
Terminal equipment monitor selection principle
The choice of monitor is mainly based on the camera selected. The criteria chosen should first consider the clarity of the selected camera and whether it is black and white or color. In terms of the sharpness indicator, the clarity of the selected monitor should be higher than that of the selected camera. It is generally considered that if the camera's sharpness indicator is 400 lines, it is sufficient to use a monitor with a resolution of 400 lines. In fact, if you configure this, the image clarity will be only about 300 lines. This is because the so-called 400-line sharpness refers to a video signal output amplitude corresponding to 400 lines on the test card when the standard test card is taken by the camera is about 40% of the corresponding video signal amplitude at 100 lines. The clarity of the monitor is also defined as such. So matching them will make the video signal output at 400 lines only 16%, and 40% will move down to 300 lines. Therefore, in order to fully display the clarity performance of the camera, a monitor with a higher resolution should be used. Although the price is more expensive, it can fully demonstrate the advantages and indicators of the system.
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