Key points of choosing security door

The demand for metal detection gates with high detection degree includes the following factors:

The uniformity of (1) magnetic field is the key to the detection rate of 100%.

(2) The security inspection and search must be strong enough to find any harmful metal object, regardless of its entry position and angle;

(3) The safety detection force must be sufficient to detect the inspected personnel at any speed;

(4), to have the ability to detect ferrous metals and nonferrous metals at the same time.

4. High-level identification.

It is required to distinguish a small amount of harmful metal objects (such as light weapons) from all kinds of metal objects carried by individuals.

Resolution is based on the following factors:

(1), uniformity of magnetic field distribution;

(2) Various analytical abilities of metallic substances;

(3), anti-interference ability of external motor noise;

(4) Free from external mechanical interference;

3. Excellent immunity (noise interference)

Noise interference is an important reason that affects the performance of metal detection door. And noise interference is divided into the following types:

(1) Instantaneous noise: noise generated by motor, electric lock and * * load on power line;

⑵ Intermittent noise: RF noise generated by power supply equipment on voltage;

(3) Noise generated by other adjacent metal detectors;

(4) Noise generated by moving or vibrating metal mass.

4. Equipment adequacy ratio

To consider the appropriate rate of equipment, we can observe from two points:

(1) Whether SMD technology is used to assemble electronic substrates;

(2) Whether to test the function of the host of the control panel.

An efficient metal detection door, in addition to the above characteristics, has different requirements for the safety of use, the simplicity of operation and the practicability of products.

What kind of products are suitable for very large-flow security inspection?

At present, some advanced metal detection doors still have their own advantages in function. Taking civil aviation airports as an example, civil aviation units in various countries have formulated new security standards for metal detectors. These standards require that micro weapons, including magnetic, non-magnetic and mixed alloy materials, can be detected. In the portal tunnel, 100% coverage space is not allowed to have detection dead angle. Because weapons and personal metal objects are often mixed and carried on the human body, false alarms are not allowed, which is a great challenge to the metal security inspection technology. Moreover, some companies have developed metal detection doors, which can be displayed in multiple sections and are recognized as better products. This kind of products can generally achieve the following points in security inspection and search capabilities and operational functions:

(1) Warning light with high visibility, which can be displayed in two directions and can detect weapons passing in two directions;

2. Plug-in setup system, which can directly select international safety standards and safety levels;

(3) For personal items with high recognition;

(4) The structure is firm and durable;

5], near-end or remote programmable input;

[6], in line with the convenience of the disabled. How to identify the quality of security doors

Metal detection doors (security doors) are the first-line equipment and facilities to control regional security, which are used to check and filter harmful and offensive metals such as knives, guns and bombs. In addition to becoming the necessary security inspection equipment at the airport, it is also widely used in prisons, large stadiums, exhibition halls, banks, courts, mint, treasury, government agencies, embassies, military and police units, telecommunications rooms, various precious metal industries, electronics industries, entertainment places and so on. It is necessary to protect the safety of people and places to avoid hijacking, dangerous security and theft.

China imported foreign security gates in the early days, which were mainly used for airport security. Due to the high price and high maintenance cost, many enterprises and institutions in need are restricted from buying security doors. China successfully developed and put it on the market in 1993, and its production and sales volume continued to increase. In order to standardize production, the Ministry of Public Security has successively issued two sets of mandatory production inspection standards, GB1521994 and GB 152 10-2003. The latter is a supplement to the former, which puts forward stricter and more detailed restrictions on the quality, detection ability and the influence of magnetic induction on human health and safety.

Because the market of this kind of products is very imaginative and attractive, the production enterprises of safety inspection doors in China are booming. At present, there are more than a dozen enterprises producing security doors in China, and their products are sold all over the country. Due to the production technology of various security door manufacturers, the product quality varies greatly. Some enterprise products can only pass the old national inspection standard GB1521KLOC-0/994, but cannot pass the new national inspection standard GB 152 10-2003. The main reason is that the production technology, raw material quality and production technology of the enterprise are inferior, so it has not obtained the production license issued by the local public security department and has become what the public calls "three noes" products. However, this inferior product is flooding the market at a very low price, and deliberately exaggerates the functions of the equipment and the functions that are difficult to verify in the process of advertising and sales, causing misunderstandings to users, so that users can't really choose safe, qualified, applicable and effective products. Why is the quality of most domestic security doors like this? The technology, performance and technology of this kind of products are analyzed and compared below, which can be used as a reference for enterprises and institutions that need safety doors.

First, the alarm principle of security door

The security door can give an alarm to passing metal objects because the door panels on both sides are equipped with sensors that can emit and receive alternating electromagnetic fields. When the metal conductor is excited by alternating electromagnetic field, eddy current will be generated in the metal conductor, and the magnetic field generated by the current has the same frequency as the original magnetic field, but the direction is opposite. The metal detector detects whether there is a metal object nearby by detecting whether the eddy current signal exists. The transmitter emits excitation electromagnetic waves, and the receiving sensor receives signals from metal objects. The signal generated by the eddy current detected by the receiving sensor, after a series of amplification processing by the circuit, will give an alarm in the form of sound and light when the signal amount reaches the set value.

In today's international market, there are two popular electromagnetic field emission signal modes for security doors:

1, sine wave: The advantages of sine wave transmission mode are simple signal processing, low cost and high sensitivity; The disadvantage is that it is easily disturbed.

2. Pulse wave: the pulse transmission mode is opposite to the sine wave transmission mode, and the signal processing is complicated and the cost is high; The advantage is strong anti-interference ability.

At present, the technology of multi-position security doors produced in the domestic market is copied from one or two earliest R&D manufacturers, who failed to protect intellectual property rights in time, so they all adopted the original sine wave emission method. In principle and signal processing mode, the basic production technologies, processes and materials tend to be homogeneous. Throughout the domestic security door manufacturers, only a few enterprises have real product development capabilities. Some enterprises have not really mastered the technology of the core parts such as the accuracy and firmness of the transmitting and receiving coils (receiving sensors), and do not know what kind of pulse and sinusoidal transmission signals to collect. They also used the original manual winding method, and the winding tightness and number of turns of the coil did not meet the industry standards. Therefore, users failed to report or report when using the products of these enterprises. Therefore, it is almost unimaginable to balance the relationship between sensitivity and anti-interference ability without exquisite production technology and long-term experience accumulation.

Some users mentioned that "digital technology" has been really applied to the manufacturing technology of metal detectors? In fact, digital coding in general means digital coding of signals, and all signals processed by digital devices are digital signals. After a certain arithmetic processing, the signal is transmitted to the terminal equipment through the medium, and then the original signal is demodulated and restored by the terminal equipment, and the signal is used to do corresponding work or analyze the signal for special function processing. In view of the fact that the working characteristics of the metal detector are sine wave or pulse wave emission, and there is no other component signal, the signal processing mode is naturally analog signal processing, and only the sensitivity control is displayed by the single chip microcomputer (for example, sensitivity 80, number of people passing through 10, number of people alarming 2 ...).

Second, when purchasing a security door, users can test the function of the security door according to the following points to identify the quality:

1. Stability detection of security door

The stability of security doors is very important, which is the first condition for customers to buy security doors. The instability of the security door will cause random alarm and missed alarm, which will make the staff at a loss and the security door will not play a real role. Because the sensors of the security door (that is, the two side plates of the door body) are open outward, it can not only emit electromagnetic waves to the external environment, but also receive electromagnetic waves generated by the external environment. There are many devices that generate electromagnetic waves in the external environment, such as high-voltage lines, large motors, electric welding machines, intermediate frequency furnaces, walkie-talkies, etc. , will radiate fusion electromagnetic field, interfere with and affect the normal detection of security doors; Therefore, all security doors will be more or less disturbed by the external environment. Manufacturers with technical strength can solve the stability of the security door itself, and at the same time deal with external interference and minimize the interference of the security door.

Usually, the security door should be designed with real-time signal intensity indicator, which can show the size of metal objects and the strength of interference signals. Real-time signal indicator lamp plays a very important role in initial installation and use. In the process of initial installation and use, the appropriate detection parameters can be adjusted according to the situation indicated by the signal lamp to minimize the interference caused by the external environment, thus improving the detection accuracy of the security door. Some manufacturers cancel this signal light to hide people's eyes and ears, or turn it off when no one passes, so that users think that the security door is working normally; As everyone knows, the security door is already in an unstable state at this time, and you will call the police whether you carry metal or not. The working parameters of the security door with signal intensity indicator can be adjusted according to the interference intensity during installation, so as to eliminate the influence of external interference on the security door and ensure the normal work of the security door. The security door has the function of environmental self-inspection, which effectively realizes anti-interference and anti-interference.

Choose to test in the same environment (including the same electromagnetic interference between power supply and external environment): turn on the machine, shield the infrared radiation device, and remove the infrared limit alarm function. Set the alarm sensitivity to a more sensitive (higher) level and let the safety door wait for the alarm. At this time, observe the number of flashing lights. If there are a large number of lights, or even random alarms, you can try to change the working frequency of the security door to avoid the interference of external adjacent frequencies until the lights are at least lit. If the working frequency is changed, the security door is still unstable or even gives an alarm at random, which shows that the security door itself has poor stability and anti-interference ability. It is necessary to compare various types of security doors one by one, and choose the best one under the same detection ability (detecting the same metal objects).

2, the ability to detect metal objects.

Select the same metal sample to test the security door, and the smaller the omission, the better.

Conventional security doors should be able to detect all metals (except specially designed detectors) and pass the strict test of "sensitivity" standard in GB 152 10-2003. The metal samples we choose to test should be included in the scope of national standards.

Metal signal detection ability is a sign of the technical strength of metal detector manufacturers. A well-skilled manufacturer can detect both nonferrous metals and ferrous metals, and even smaller metals with good stability, with clear sensitivity control. If the sensitivity of poor quality security doors is slightly improved, they will call the police and do not bring anything through. If the sensitivity is slightly reduced, many metal objects will pass before calling the police. This kind of safety door is caused by poor internal circuit design performance and nonlinear control, so it cannot be used.

In addition, due to the directivity of electromagnetic waves, the detection of metal objects is also directional, and the signal generated by cutting the surface with the most electromagnetic waves is relatively strong, while the signal generated by cutting the surface with the least electromagnetic waves is relatively weak. Excellent production enterprises can homogenize the directionality of the magnetic field, so there is little difference in the effect of detecting metal objects in all directions in the same detection area of the security gate; If the difference is large, the bigger the omission is, so users should choose products with good directional detection and balance effect.

Select the same metal object to be carried by the tester through all positions of the security gate, pass through the metal object in all positions and in different directions, and select products with less missed detection. For small metals to be excluded, it is only necessary to adjust the sensitivity to a suitable position when detecting larger metals. The test method is the same as above.

3, security door shell

The material of door frame is also one of the important links that affect the quality of security doors. Because the amount of signal generated by the detected metal in the safe electromagnetic field environment is very small, signal processing usually needs to be amplified by tens of thousands of times to meet the requirements of circuit driving. Even if the front-end sensor has only a small displacement change, it can also cause an alarm after being amplified by the circuit, so it is required that the deformation of the security door shell should be as small as possible during long-term use.

The security door is designed as an independent door frame, and the door panel equipped with sensors is thin and long, with a thickness of only five or six centimeters (5cm-6cm) and a length of more than 220 centimeters (220CM). Due to the installation environment and long-term working relationship, the door panel is easy to deform, which makes the parameters of the sensor differ too much from those of the factory, which affects the detection effect and cannot work for a long time. At present, most domestic manufacturers use wood particleboard or high-density wood fiberboard as the security door shell; As we all know, wood particle board or high-density wood fiber board is very easy to absorb moisture, and will be deformed, dispersed and disintegrated after several months; Especially in coastal areas, due to humid air and long rainy season, the products can not be used for a short time after purchasing these security doors. Good security door manufacturers attach great importance to product quality. For example, the shell is made of high-strength PVC and the door frame is made of aluminum alloy. This material is not easy to deform and get wet, which ensures that the product can be used normally for a long time, and its product carrier needs no maintenance after ten years of use.

In addition, some enterprises use a lot of metal decorative materials to decorate the shell for the sake of beautiful products. Because the security door is specialized in detecting metal objects, such as a large number of metal decorative materials, it is an extremely unstable factor. Sometimes due to the wind resistance when people pass through the security door, the door panel vibrates, and the metal on the door frame and the receiving sensor are displaced, which leads to random alarm. These enterprises can't make a breakthrough in metal detection technology, so they make a fuss about appearance and fancy functions and attack the low-end market with low-price strategy. It has strong earthquake resistance. When shaken by external force, it will not report indiscriminately like other security doors. At this time, the words "anti-vibration" will be clearly displayed on its LCD screen. High-level users still focus on quality, performance and safety when purchasing, and price is a secondary factor.

4. Electromagnetic radiation safety verification.

Many household appliances, such as mobile phones, walkie-talkies, microwave ovens, induction cookers, televisions, etc. , will radiate electromagnetic waves to the surrounding space, and there is a similar situation in the walk-through metal detection door. The intensity of electromagnetic wave is measured by the intensity of electromagnetic induction. When the magnetic induction intensity exceeds a certain value, it will cause harm to people.

In order to ensure the safety of the inspected personnel and operators, the Chinese national standard GB 152 10-2003 "General technical conditions for walk-through metal detection doors" strictly limits the magnetic induction intensity of walk-through metal detection doors. For relevant technical parameters, please refer to the description in 4.6.6 "Limit value of magnetic induction intensity in detection area" in the national standard "In the area formed by inward 150mm of the left and right boundaries of the detection area, the magnetic induction intensity at any point should not exceed 30μT". Only when it does not exceed the value specified in the standard can personal health be protected from harm. Therefore, the security door produced by any enterprise must strictly implement the national standards, and pass the inspection of the "Quality Inspection Center for Security and Police Electronic Products of the Ministry of Public Security" to explain the safety of its electromagnetic radiation and issue a certificate, and the local public security department will issue a production license accordingly. Therefore, the magnetic induction intensity must be lower than the warning value of national standards to ensure the personal health and safety of the inspected personnel and operators.

Security inspection is a responsible undertaking and a combination of ideas and technologies. This field is very extensive and needs professional and socially responsible practitioners. At present, the quality of products and users in China security door market is not synchronized, and most users are non-professionals, who know little about the equipment principle and using skills. Moreover, anti-theft door products have been widely used in various public places, enterprises and institutions, so a large number, intensive and routine use in the public. If you use some inferior products that do not meet the requirements of product safety and quality, it will bring extremely unstable factors to social security, which is a shame and worry for the security door industry.

Therefore, in order to strengthen and accelerate the formulation and implementation of industry standards, strengthen market supervision, and carry out strict conformity assessment and compulsory certification, not only traditional safety certification, but also product-specific performance certification (such as the impact of magnetic induction radiation intensity on personal health and safety in metal detection, and waterproof performance, etc.). ). Raise the threshold of production and market entry, standardize product promotion, crack down on false advertisements, form orderly market competition, and reflect the social responsibility of practitioners.