Archway walk-through Metal Detectors (AMD), also known as Walk-Through Metal Detectors (WTMDs), portal or personnel screening metal detectors, are a security screening device that uses electromagnetic fields to detect metal objects concealed on individuals passing through an archway-shaped portal. They are widely used in the security of building entrances, prisons, airports, hotels and banks, as well as for other venues and events.
Unlike time-intensive manual searches or handheld metal detector screening, walk-through metal detectors enable efficient, hands-free screening of hundreds of people per hour whilst maintaining high detection standards. This combination of thoroughness and speed makes them essential for modern security operations
The system analyses metal objects and offers good recognition of personal items such as coins, keys, and belt buckles. It has high detection sensitivity for both magnetic and non-magnetic metals. The multi-layered coil design and high-brightness LEDs accurately show the horizontal position of any metal objects. This speeds up subsequent operator intervention.
How Do Walk-Through Metal Detectors Work?
Walk-through metal detectors operate by generating electromagnetic fields within the archway portal and monitoring these fields for disturbances caused by metal objects.
When a person carrying metal passes through the detector, the metal disrupts the electromagnetic field, triggering an alarm that alerts security personnel to conduct further screening.
Basic Operating Principle:
1. Electromagnetic field generation – The archway metal detector creates a controlled electromagnetic field between its vertical panels.
2. Field monitoring – Sensitive receivers continuously monitor the field’s characteristics.
3. Metal detection– Metal objects passing through the field cause measurable disturbances.
4. Signal processing – Advanced electronics analyse these disturbances to determine metal presence, size, and location.
5. Alarm activation – When metal exceeding threshold settings is detected, visual and audible alarms activate.
6. Zone indication – LED indicators show the vertical location of detected metal, guiding security personnel.
Types of Walk-Through Metal Detector Technologies
Archway walk-through metal detectors typically use one of three sensing technologies to identify metal objects. All of these detect changes in magnetic fields caused by metal objects passing through them. Many older systems relied on the Earth’s magnetic field, but the detection field can also be produced by the archway metal detector itself.
Pulse induction (PI) detectors generate a time-varying or pulsed magnetic field that creates an electric current in metal objects as they pass through the archway. This current produces a separate magnetic field, which is picked up by the detector. The system recognises this as a metal object. PI detectors can sense both ferrous (iron-containing) and non-ferrous objects such as aluminium, brass, bronze, and copper.
Continuous wave (CW) detectors are similar but transmit an oscillating magnetic field. The detector analyses changes in the phase and amplitude in the resulting magnetic fields to spot the presence of any metal objects. CW detectors also detect both ferrous and non-ferrous objects.
Passive detectors sense the interaction between any metal and the Earth’s magnetic field. This type of detector can only sense ferrous metal objects. Aluminium and other non-magnetic metals are not magnetised by the passive Earth’s field and cannot be sensed this way.
What Do Walk-Through Metal Detectors Detect?
Most walk-through metal detectors can detect both ferrous (iron-containing) and non-ferrous metals, depending on the detection technology employed.
Some of the items that metal detectors can pick up include:
Threats:
- Firearms and ammunition.
- Knives, blades, and edged weapons.
- Improvised weapons (such as IEDs)
- Prohibited items (large metal tools, contraband)
Common items that may trigger detection:
- Keys, coins, belt buckles (personal items)
- Mobile phones and electronics
- Jewellery and watches
- Medical devices and mobility aids
Perhaps unexpectedly, the mass of an object is not particularly significant in metal detection. The foil in a pack of cigarettes could set off a detector despite its small mass. Metal detection depends on an object’s size, motion, shape, electrical conductivity, magnetic properties, surface area and alignment.
To learn more about what metal detectors can and cannot detect, read our guide ‘What Do Security Metal Detectors Actually Detect? Beyond the Basics’.
Are Walk-Through Metal Detectors Safe?
Some people worry about possible health side effects from metal detectors, particularly for pacemakers.
Walk-through metal detectors are completely safe for all individuals, including those with medical implants, pregnant women, and children. Despite common concerns, these systems pose no health risks and operate well within established safety guidelines for electromagnetic exposure.
In fact, the tiny electrical fields that are produced by walk-through metal detectors are much weaker even than a humble hair-dryer. The fields are simply not strong enough to be of concern, even to patients with pacemakers.
Understanding how walk-through metal detectors work and what they detect helps organisations select systems appropriate for their own security requirements and operations.
Walk-Through Metal Detectors from 3DX-RAY
3DX-Ray’s AXIS™-A33 represents advanced walk-through metal detector technology, combining high sensitivity with intelligent discrimination to offer both security effectiveness and efficiency.
The AXIS™-A33 archway metal detector features 33 independent detection zones, significantly more than basic systems offering 6-18 zones. This granular coverage enables:
- Precise horizontal location identification of detected metal.
- Reduced false alarms through zone-specific sensitivity.
- Faster secondary screening by pinpointing metal location.
- Enhanced detection of multiple small objects versus single large items.
For detailed specifications and consultation on implementing walk-through metal detector systems in your security operations, 3DX-Ray’s specialists provide guidance tailored to your specific requirements.