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First, explosion-proof principle
The principle of application of explosion-proof equipment is generally gap-type, contact-proof type, the use of safety measures and other features such as the use of explosion hysteresis characteristics to support the other advanced explosion-proof principle. Among them, there are gap-proof explosion-proof principles for television systems and explosion-proof principles using safety measures.
1. Gap explosion protection principle EDM and arc can ignite explosive mixtures. The gap-proof flameproof structure established by Germany is a more reliable method of preventing arcs and other ignition of surrounding explosive mixtures. Shenzhen Shiguo's explosion-proof camera shroud adopted this method and played an explosion-proof role. It has a sufficiently strong enclosure that withstands the maximum explosion pressure generated by the internal explosive gas mixture, ensures no deformation or damage, and has a structural gap to allow the injected combustion products to cool down below the outside through a certain flange length The autoignition temperature of the explosive mixture. The structural gap can be composed of a plane joint surface or a cylinder joint surface, and can also be composed of a curved path, a thread or a barrier type structure. In addition, structures such as microholes, mesh covers, laminations, sand-filling, etc. also fall into the explosion-proof form of this principle.
2. The explosion-proof principle using safety measures adopts a series of safety measures on the equipment so that it will not generate sparks, arcs or dangerous temperatures to the maximum extent, or the sparks, arcs or temperatures generated by effective protection elements cannot ignite. Explosive mixtures, to achieve the purpose of explosion-proof, explosion-proof increase safety, intrinsically safe and other electrical equipment are manufactured using this principle.
Second, the material of explosion-proof equipment
For explosion-proof explosion-proof equipment enclosures should be able to withstand 1.5 times the actual maximum internal explosion pressure, but not less than 3.5 × 105Pa. Equipment used for Class I mining face shall be made of steel plate or cast steel. Class I equipment for non-excavating face shall be available with a brand no less than HT25-47 grey cast iron; Class I portable equipment and Type II equipment can be made of a light alloy with a tensile strength of not less than 117.6N/mm2 (12kg/mm2) and a magnesium content of not more than 0.5% (by weight). The shell material of the essential equipment can be made of a light alloy with a magnesium content of not more than 0.5% by weight or a plastic with a surface resistance of not more than 1 x 109.
Third, the sign of explosion-proof equipment
Explosion-proof equipment must be printed with the product's explosion-proof signs. Clear and permanent embossed signs “Ex†should be provided at the obvious places of the equipment housing. At the same time, the nameplate should be set and fixed reliably. There should also be explosion-proof type signs on the equipment. Common explosion-proof types include explosion-proof type “dâ€, intrinsically safe “ia†and “ibâ€, increased safety type “eâ€, positive pressure type “pâ€, and oil-filled type. “oâ€, sand-filled “qâ€, non-spark type “nâ€, encapsulated “mâ€, hermetically sealed “hâ€, special type “sâ€, dust-proof “DIPâ€, etc. Category and gas class (Type I is the denser methane environment in the mine, Type IIA is an explosive gas mixture environment such as ethane, propane, carbon monoxide, methanol, and gasoline, IIB is an explosive gas mixture environment such as gas and ethylene, and IIC is hydrogen, Acetylene and other explosive gas mixture environment), temperature group (generally there are T1, T2, T3, T4, T5, T6 and other six groups, the temperature from high to low, indicating that the maximum surface temperature of the device is not allowed to exceed the value), etc. Explosion-proof certificate number; production date, product number, product standard must indicate the content must be noted. For example, the explosion-proof mark on a world explosion-proof camera is "ExdIICT6". It means that the explosion-proof camera is explosion-proof and can be used in an environment containing explosive gas mixture of hydrogen and acetylene. The maximum surface temperature of the equipment cannot exceed. 80°C.
At present, the market competition of explosion-proof cameras is very fierce, although we can determine whether or not an explosion-proof camera meets its requirements through explosion-proof grades and national certification levels. However, there are many manufacturers who often use brand-name curtains, shoddy, and hold prices. To mislead customers and make many engineering companies deceived. Therefore, here, Xiao Bian reminds customers who are interested in purchasing explosion-proof cameras to polish their eyes, verify the product's grade certificate, and review more reviews on the product to see which product level they prefer. In general, it is definitely a grade. The higher the explosion-proof performance, the higher the price.
Explosion-proof camera resolution technical analysis
When it comes to explosion-proof cameras, it is unavoidable that several parameters such as pixels, lines, and resolution are used to measure resolution. However, many of the contractors did not understand the three parameters when they purchased explosion-proof cameras. Some people did not even know their concepts. This is understandable, because many suppliers in the provision of products to the project, because of the time, coupled with the relationship between parameters and product transactions does not have much impact, so suppliers and contractors generally only negotiate the number of pixels It does not involve the relationship between pixels, lines, and sharpness.
To a certain extent, the parameters of the explosion-proof camera's pixels, lines, and resolution are the same as the relevant parameters of computer monitors, televisions, and mobile phone displays that are commonly used by people. The three are all images of explosion-proof cameras. The description of textures is conducive to understanding the image quality of explosion-proof cameras from various angles. This is one reason why many people cannot understand the relationship between them. Then, here, Worldcraft Technology, as a professional manufacturer of explosion-proof cameras, will provide you with a detailed explanation of the relationship between the three, and provide a reference for engineering companies and people who are interested in learning.
The first is the pixels of an explosion-proof camera. It is the basic element that constitutes an image. The surveillance image of an explosion-proof camera consists of successive and rapidly appearing images, which consist of one pixel. It's equivalent to magnify an image a lot of times, then divide it from left to right and from top to bottom, it is regularly divided into many grids, fill a color in each grid, and then reduce the image to its original size. It forms an image we usually see. These grids are equivalent to pixels. The number of pixels is generally determined by the manufacturer. The more pixels, the finer and clearer the image, ie, the higher the resolution.
After knowing the pixels of the explosion-proof camera, let's talk about the clarity and the number of lines. The resolution we usually refer to includes horizontal resolution and vertical resolution. The number of image pixels can be obtained from these two indicators. We still use lattices to illustrate that an image is divided into many rows and many column grids. How many pixels are there from the left to the right in the same row of the grid? This is called horizontal definition. How many pixels are formed in the same column grid from top to bottom? It is called vertical resolution. Since each row of cells forms one pixel in the vertical direction, we can also say that "vertical resolution" is the number of "horizontal scan lines" that an image consists of. Shiguo Science and Technology Chuangxin stated that the number of horizontal scan lines in an image is determined by the signal format, so as long as the signal format is determined, the vertical resolution is determined. For PAL, the last vertical resolution you see is 625. Further, the picture we see is not composed of all 625 lines. In fact, there are 49 lines for transmitting other information such as closed captions, texts, test signals, etc. It also takes some time when the electron beam goes from the bottom to the top to begin scanning the next image. To remove the number of rows that we "invisible", we see a picture that actually consists of a maximum of 576 lines. This is also the highest vertical resolution of the PAL system. Further, due to the imaging reasons and human visual characteristics, these 576 lines are only the theoretical resolution. The actual vertical resolution of the image you "see" must also be multiplied by a correction factor less than 1, which is called the Kell coefficient. For interlaced scanning, the Kell coefficient is 0.7, so for the PAL system, the vertical resolution of the last displayed image is about 400 lines. When actually viewing the test chart, the observed vertical resolution can usually reach about 450 lines because the Kell coefficient is not considered.
The vertical resolution is completely determined by the signal format, which is very easy to understand. Horizontal definition is the most easily confusing concept. The biggest problem is that there are multiple expressions of horizontal definition. In the field of video surveillance such as explosion-proof cameras, we are more accustomed to using the "per image height" of pixels to represent horizontal resolution, or "television lines." The origin of this habit dates back to 60 years before the television was born. At the time, because the format of the signal had determined the vertical resolution of the image, the experts' idea was to represent horizontal resolution in a manner that was related to vertical clarity. In other words, whether it is clearer in the horizontal direction or clearer in the vertical direction can be clearly seen through this relative clarity. For this reason, horizontal definition is defined as the number of pixels that can be displayed in the horizontal direction that is equal to the screen height. The definition obtained under this definition is called the "TV line", which is the so-called line number. Therefore, when you still hear how much clarity a video signal has, it doesn't mean how many pixels are from the leftmost to the rightmost edge of the image, but how many pixels are in the same horizontal width as the height of the image.
The image transmitted by the explosion-proof camera is not a boxy one. Generally, the display ratio is 4:3 or 16:9. That is, to achieve the same horizontal resolution as the vertical resolution, the pixels in the horizontal direction should reach 4/3 or 16/9 times the vertical resolution. Image sharpness = image quality of the signal source × processing level of the processing circuit × development quality of the display method. All three factors are equally important in determining the final image quality. Any difference in the links will result in a decrease in the horizontal resolution of the final image. Even if some products improve the processing circuit performance or the display performance, the image quality cannot be significantly improved without the corresponding signal source cooperation. Shiguo Technology Huanggong explained that the HD explosion-proof monitoring system requires not only a million HD explosion-proof surveillance cameras, but also the back-end processing and display of high-definition, so that performance can play better.
Similarly, as an indicator of the clarity of the explosion-proof camera monitoring picture, the three indicators of pixel, line number, and clarity may seem redundant to the contractor and the user, but for each professional manufacturer, these three indicators are: Indispensable is the measure of explosion-proof camera manufacturers tailor-made for the market. However, it is worth affirming that in the same product, any one of the three indicators will change, and the other two indicators will also change. This is why the relationship between the three is rarely paid attention.
Explosion-proof cameras, perhaps a lot of people's first consciousness is to protect the surrounding environment from the explosion of the camera, but the real sense of the explosion-proof camera is to prevent the explosion of the internal camera caused the explosion of the external environment, these two meanings may be a bit difficult to understand, or It is vague and confusing, but it is a completely different concept.