The concept of metal detection is one we often take for granted. Between the familiarity of walking through one at TSA screenings to the popularity of metal detection as a hobby amongst beachcombers, the technology and its application is very much a part of everyday life.
This is to say nothing of the crucial role metal detection plays in the manufacture of materials and the safety of other industrial processes.
But the principles behind metal detection, and the ways in which they operate, are not well-known to the average person.
As someone in an industrial or manufacturing role, it would help you to understand how these detectors work – and just how central a role they play in the safety of industrial systems and processes.
Metal Detection – Principles and Uses
Metal detectors are, as the name suggests, devices that are capable of detecting the presence of metal within a certain range or field.
They do this via the principle of electromagnetic induction, using systems called magnetic pickups to detect the presence of a conductive metal material. How these pickups work will be examined shortly, but first there are two key areas in which metal detectors prove useful:
Security Screening
Since September 11th, 2001, airport security has been a paramount concern for the US government and for the private entities operating in US airports.
Metal detectors are an essential part of the security process here, used as they are to alert TSA agents to the presence of metal materials on a traveler’s person.
The traveler passes through a gate containing metal detecting magnetic pickups, whereupon an alarm is sounded at the presence of metal material. This enables the airport to ensure weapons do not make it onto a flight without permission.
Industrial Processes
Any multi-step industrial process invites risk in the form of contamination. Machinery and equipment can be sensitive to foreign or unexpected objects, resulting in failure at best and injury at worst.
For example, a food processing plant could see metal debris fall into a product, which could then go on to injure a consumer. Metal detectors prevent such occurrences, allowing workers to halt production and remove defective products before they make it to the superstore shelves.
Magnetic Pickups and Their Role
Metal detection is only made possible by a specific component, called the magnetic pickup.
These components use electromagnetic induction to detect the presence of a conductive material; disturbances of a magnetic field generate a current in wire coils, which can then be measured and amplified by additional circuitry in order to trigger an alarm or emergency stop system.
The foreign metal material receives a light magnetic field of its own via the metal detector, the movement of which then generates a current.
This simple principle is used in many areas besides metal detection – most famously, perhaps, in instruments such as the electric guitar.
The movement of strings over a magnetic pickup assembly generates a sinusoidal current corresponding to the rate of vibration, reproducing the tone of the string electrically.
