Walk-Through Metal Detector

Overview

A walk-through metal detector is a fixed archway that screens people for metal as they pass between its two upright pillars. Each pillar, the Left Side Panel and the mirror-image Right Side Panel, is a composite shell over an aluminium frame that holds a coil stack. One pillar's coils are driven; the other's sense the field, and the electronics read how that field is disturbed.

The unit reports detections by vertical zone, so an operator sees roughly where on the body the metal sits. The Zone Display lights an LED bar at the matching height, while a tone from the Alarm Unit and a header strobe signal the event. Operators set sensitivity and programs from the Operator Control Panel, and a Traffic Counter tracks how many people passed and the alarm ratio.

The whole archway stands on a Floor Base with levelling feet, and a single Power Supply with battery backup keeps it screening through brief outages.

How it works

This detector uses pulsed induction. The Transmit Coil is driven with short, sharp current pulses, each launching a magnetic field across the passage. When a pulse ends, the field collapses abruptly. Any conductive metal in the archway carries induced eddy currents that decay more slowly than the field itself, and that lingering decay is exactly what the receive side looks for.

The Receive Coil is split into six vertical windings, so each body height is sampled independently, that segmentation is what gives the per-zone resolution. The faint decay signals are pre-amplified on the panel's coil board, then carried to the Control Unit. There a multi-channel ADC digitises every zone and a DSP correlates each decay curve against stored signatures, separating threat-grade metal from coins, keys, and belt buckles according to the selected program. When a zone crosses threshold, the DSP fires the alarm and the matching LED bar in the same processing cycle, so the alert tracks the person as they walk through.