Sodium Formate (English name Sodium formate; Formic Acid sodium salt), also known as sodium formate, contains two crystal waters in the crystal, so it is also called sodium formate dihydrate, sodium formate dihydrate, sodium formate dihydrate (Sodiumformatehydrate). Sodium formate is one of the simplest organic carboxylates. It is white crystals or powder with a slight Formic ACID odor. Slightly deliquescent and hygroscopic. Soluble in about 1.3 parts of water and glycerin, slightly soluble in ethanol and octanol, insoluble in ether. Its aqueous solution is alkaline. When heated, sodium formate decomposes into hydrogen and sodium oxalate, and then generates sodium carbonate. Sodium Formate Sodium Formate,Sodium Formate Structure,Formula Of Sodium Formate,Formula Of Sodium Formate ZIBO JUNTU INTERNATIONAL TRADE CO.,LTD , https://www.juntuchem.com
The size of the focal length determines the size of the viewing angle, the focal length is small, the angle of view is large, and the observed range is also large, but the distant objects are not clearly distinguished; the focal length is large, the viewing angle is small, and the observation range is small. As long as the focal length is chosen properly, even distant objects can be seen clearly. Since the focal length and the angle of view are one-to-one correspondence, a certain focal length means a certain angle of view. Therefore, when selecting the lens focal length, it is necessary to fully consider whether the observation details are important, or whether there is a large scope of observation. If you want to see the details, choose a long-focus lens; if you look at a close-up scene, choose a small-focus wide-angle lens.
2. Optical coefficient
The luminous flux, denoted by F, is measured by the ratio of the lens focal length f and the clear aperture D. Each lens is marked with a maximum F value, for example 6mm/F1.4 represents a maximum aperture of 4.29 mm. The luminous flux is inversely proportional to the square of the F value. The smaller the F value, the greater the luminous flux. The index of the aperture index sequence on the lens is 1.4,2,2.8,4,5.6,8,11,16,22, etc. The rule is that the exposure value of the previous standard value is exactly the value of the exposure value of the next standard value. Times. In other words, the clear aperture of the lens is 1/1.4, 1/2, 1/2.8, 1/4, 1/5.6, 1/8, 1/11, 1/16, and 1/22. The previous value is The root value of the latter value is 2 times. Therefore, the smaller the aperture index is, the larger the clear aperture is, and the larger the illumination on the imaging target surface is. In addition, the aperture of the lens is divided into MANUAL IRIS and AUTO IRIS. With the camera, the manual iris is suitable for occasions where the brightness changes little, and the amount of light entering it is adjusted by the aperture ring on the lens, so that it can be adjusted once and for all. The automatic iris lens automatically adjusts to changes in light, and is used in outdoor and entrance lighting applications where light changes frequently and frequently.
3, automatic aperture lens
Automatic aperture lenses currently fall into two categories: one is called video (VIDEO)-driven, and the lens itself contains an amplifier circuit that converts the video amplitude signal from the camera into control of the iris motor. The other type is called a direct current (DC) drive type and uses the DC voltage on the camera to directly control the aperture. This lens contains only a galvanometer iris motor and requires an amplifier circuit inside the camera. For various types of auto iris lenses, there are usually two adjustable knobs, one is ALC adjustment (light metering adjustment), there are two options for the peak light metering and average light metering according to the target lighting conditions, generally take the average light metering file; The other is LEVEL adjustment (sensitivity), which can brighten or darken the output image.
4th, zoom lens
Zoom lens is divided into manual (MANUAL ZOOM LENS) and electric (AUTO ZOOM LENS) two, manual zoom lens is generally used for scientific research projects and not used in closed-circuit surveillance systems. When monitoring large scenes, the camera is usually used in conjunction with the electric lens and the head. The advantage of the electric lens is that the zoom range is large. It can not only look at a wide range of situations, but also can focus on a certain detail. In addition, the pan and tilt can be rotated up and down and left and right, and the visible range is very large. The electric lens has 6 times, 10 times, 15 times, 20 times and other magnifications. If you know the reference focal length, you can determine the variable range of the lens focal length. For example, a 6x motorized lens with a reference focal length of 8.5 mm, the zoom range is continuously adjustable from 8.5 to 51 mm, and the field of view is 31.3 to 5.5 degrees. The control voltage of the electric lens is generally DC 8V~16V, and the maximum current is 30mA. Therefore, when selecting the controller, fully consider the length of the transmission cable. If the distance is too far, the voltage drop generated by the line will cause the lens to be uncontrollable, and the input control voltage must be increased or the video matrix host must be replaced to match the decoder control.
1, focal length