Walk Through Metal Detector working principle and common problems and solutions

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Walk Through Metal Detector working principle and common problems and solutions

Walk Through Metal Detector is a detection device that can detect whether a person carries a metal object, also known as a metal detection door. It is mainly used in airports, stations, large conferences and other public places with a large flow of people to check the hidden metal objects on people's bodies, such as guns and control knives. When the inspected person passes through the metal detection door and carries the metal weight, the quantity exceeds or the parameter value of the shape index, the safety door will immediately alarm and display the location of the metal that caused the alarm, and the cavalier safety personnel can quickly find the metal object carried by the person.

Walk Through Metal Detector principle

1.The crystal oscillator generates a 3.5-4.95M sinusoidal oscillation, and the frequency divider divides the frequency into approximately 7.8K sinusoidal waves.The power of the triode and the coil is amplified and input into the large coil (region 7) of the door panel for electromagnetic wave transmission.The coils in zones 1-6 are received separately. After receiving, compare the received signal with the reference signal and send After changing the current, change the output level of the capture card. The CPU executes the data acquisition of 6 area acquisition cards within 300 milliseconds. Scan to determine the location of the metal and display the output.

2. Structure:

Door structure: it consists of 1 large coil, 6 small coils, compensation coil and graphite.

3. Work process in the detection process:

CPU detection → a group of infrared is blocked → detect whether the data of each acquisition card has changed → alarm → Detect another set of infrared rays → reset and re-detect.

Common Problems and Solutions of Walk Through Metal Detector

1. Can detect objects:

Generally, magnetically conductive metals are objects that are easily attracted to magnets, such as silicon steel, iron, copper, alloys, and other objects. However, if objects are scattered, such as powdered metal, linear metal, etc., it is not easy to detect. You can use dollar coins as a standard to detect metals. If the customer's material is special, you can request samples for testing.

2. Common problems:

Install and distinguish the left and right door panels, the left side (4P plug) and the right side (3P plug), the connection is firm and cannot be reversed.

When not alarming, please check whether the intensity is always bright and the infrared count is normal.

specific problem:

(1) Unable to start:

The power indicator is on. Check that the power supply in the box is plugged in. If there is no problem, please check that the fuse and power supply are properly connected.

The power indicator is off. Check whether the air inlet plug is firmly connected and the power cord is intact.

(2) Infrared does not count: Check if infrared is firmly connected and the infrared head is blocked.

(3) No alarm:

The intensity is always bright, please check if there are interference sources around, try to change the crystal to change the frequency.

Check if the infrared is normal.

(4) Long alarm time: check whether the alarm time setting and infrared count are normal.

(5) Tandem pole: check for interference.

(6) Flow phenomenon of the LCD display door: check whether the LCD display panel is squeezed, loosen the screws on the LCD display panel.


Walk-through metal detectors utilize magnetic fields to detect metal that passes through them. The science behind how they work is based on Maxwell's equations. The latest detectors include multiple detection zones allowing them to pinpoint the location of the metal causing the alarm. They have been proven to be a safe and effective method for maintaining security.

 If you need help selecting the correct walk-in metal detector, please contact us at 8615074487389 or Email:, or use our contact form.



Contact: Scarlett

Phone: +8615074487389


Add: No. 302, Building C, Xintangkeng Industrial Zone, No. 2 Qiancheng Road, Henggang Industrial Zone, Shenzhen, Guangdong, China