I. Types of security doors in supermarkets
1. principle of radio system: the radio system uses radio waves as transmitting and receiving signals, and the detection frequency range is 7.x~8.x MHz. Transmitting radio signals of different frequencies. The biggest advantage of wireless system is that the system cost is very low and the installation is very convenient. This is the first principle of supermarket security door.
2. Electromagnetic wave principle: Electromagnetic wave system uses electromagnetic wave as detection signal. Its label is the smallest and cheap, and it can be degaussed repeatedly, such as that used in university libraries. However, the system is easily influenced by magnetic or metallic substances, which is the second principle of supermarket security door.
3. Acoustomagnetic principle: The tuning fork will only cause * * * vibration when the oscillation frequency is the same. The principle of acoustomagnetism is the application of this physical principle, which realizes almost zero false alarm operation. When the acousto-magnetic system tag fixed on the commodity enters the detection area of the system, both of them will generate * * * vibration, but only when the receiver receives the * * * vibration signal for four consecutive times will it give an alarm. Acousto-magnetic system is characterized by high anti-theft detection rate, almost zero false alarm, good anti-interference, and the protection exit width can reach 3.5 meters, which is the third principle of supermarket security door.
Second, the advantages of supermarket security doors
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Third, the supermarket security door quality appraisal method
1. Effective detection rate of supermarket security doors: detecting the effective detection rate of supermarket security doors can be called blind area measurement or false negative rate. Whether it is a supermarket or a shopping mall, there will be some blind spots because of the influence of the environment. The blind area refers to the area where the anti-theft antenna cannot give an alarm when a valid tag enters the monitoring area.
2. The environment and installation distance will affect the blind area. In an ideal environment, the suitable installation distance is 90cm, and the detection label is usually a domestic 4*4 soft label. After the installation is completed, it needs to be tested repeatedly. If the missed detection rate is too high, the installation distance or surrounding environment should be adjusted appropriately.
3. False alarm rate of supermarket security door: False alarm rate is the primary performance index to measure the whole supermarket security system. False alarm is inevitable, and there are many reasons for false alarm in actual operation, some of which are impossible to find out and there is no law to follow.
4. Secondly, the causes of false positives mostly depend on the performance of the machine itself, and the traditional processing method using analog signals has relatively low anti-interference ability and is easy to cause false positives; It is best to use a single-chip microcomputer chip to process signals, except for signals similar to tags, which will basically not cause false positives; Moreover, the machine with DSP digital signal processing system has a lower false alarm rate.
I believe that every reader has a new understanding of supermarket security doors after reading the above contents. I hope you can get help after reading it. Bian Xiao is very grateful to every reader for reading. Your reading has given us the greatest support and motivation.