The Principle and Importance of Security Door Detection
A sinusoidal oscillation in the range of 3.5 to 4.95 MHz is generated by a crystal oscillator. This sine wave is then divided by a frequency divider to approximately 7.8 kHz. After being amplified by a triode and a coil, the signal is sent to the large coil on the door panel (which consists of seven zones) for electromagnetic wave emission. The door’s six area coils receive the emitted signals individually. Once received, the signal is compared with a reference signal. If any change is detected, the output level of the acquisition card changes. The CPU scans the data from the six area acquisition cards within 300 milliseconds to determine the location of the metal object and display it accordingly.
Security doors can detect passing metal objects because the two side panels are equipped with sensors that transmit and receive alternating electromagnetic fields. When a metal conductor is exposed to this field, eddy currents are induced within the metal, which in turn generate their own magnetic field at the same frequency but in the opposite direction. The metal detector identifies the presence of metal by detecting these eddy current signals. The transmitter emits an excitation electromagnetic wave, and the receiving sensor captures the signal from the metal object. The sensor then amplifies the signal through a circuit and triggers an alarm in the form of sound and light when the detected signal reaches a pre-set threshold.
In many manufacturing companies, the rising costs of raw materials such as precious metals—like copper, aluminum, tin, and nickel—have significantly increased production expenses. Industries such as hardware, electroplating, electronics, cables, and mechanical casting have seen a steady rise in the cost of finished products, semi-finished goods, and components. Due to the high value of these materials and the presence of numerous recycling points, some individuals with malicious intent may attempt to steal them. To prevent the loss of valuable metals, companies must implement effective measures. Practical experience has shown that security doors and metal detectors can be used in factories in a scientific, objective, and humane way to prevent and warn against theft. This is because security gates offer high detection accuracy, are adjustable, are free from human interference, do not require physical searches, respect employees, and are fast and easy to manage.
Public places such as discos, dance halls, and law enforcement facilities often attract large crowds, making them vulnerable to criminal activities. Individuals with harmful intentions may carry prohibited items like knives or guns, leading to serious injuries, property damage, and significant societal harm. To prevent such incidents, the use of scientific and effective management tools is essential. Security doors are among the most effective tools in ensuring safety. They are widely used in critical security locations such as airports and have proven to be one of the most reliable methods for preventing terrorist attacks over time.
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