Handheld metal detectors work by emitting an electromagnetic field and detecting disruptions to that field caused by the presence of metallic objects.
Here's a breakdown of the process:
The Basic Principle: Electromagnetic Induction
Handheld metal detectors utilize the principle of electromagnetic induction. This means that a changing magnetic field can induce an electrical current in a nearby conductor (like a metal object).
Components of a Handheld Metal Detector
A typical security wand has the following key components:
- Transmitter Coil: This coil generates an alternating electromagnetic field. This is usually achieved by sending an alternating current through the coil.
- Receiver Coil: This coil detects changes in the electromagnetic field generated by the transmitter.
- Control Circuitry: This circuitry controls the transmitter, processes the signal from the receiver, and triggers an alert (usually an audible beep or a visual indicator).
The Detection Process:
- Electromagnetic Field Emission: The transmitter coil creates an electromagnetic field around the detector.
- Metal Object Interaction: When the electromagnetic field encounters a metal object, it induces eddy currents within the metal.
- Field Distortion: These eddy currents, in turn, generate their own electromagnetic field. This new field interacts with and distorts the original field emitted by the detector.
- Detection by Receiver: The receiver coil senses this distortion of the electromagnetic field. The strength of the distortion is related to the size, shape, and conductivity of the metal object.
- Alert Trigger: The control circuitry analyzes the signal from the receiver coil. If the distortion exceeds a preset threshold, the detector triggers an alert, signaling the presence of metal.
In Summary
Handheld metal detectors operate by emitting an electromagnetic field, and then sensing changes or disturbances in this field. The presence of metallic objects near the detector causes this disturbance, which is then detected and signaled by the device.
