How can detectors tell if we are carrying any metal?

Anyone who has entered a bank or traveled on a plane knows very well: in these situations, you have to go through a metal detector. Well, it’s a security issue, but it’s still annoying when we’re blocked because we’ve forgotten our keys in our pockets. Do you want to understand why this is happening?

We tend to notice the so-called hallway, which looks like a door frame. But there are models capable of detecting metal remotely, such as portable ones used in parades or nightclubs, and those that find explosive mines in the ground.

They all operate using electromagnetism and consist of two basic elements, the transmitter and the receiver. The transmitter consists of copper wires wrapped around a metal material, supported by an external power source that creates a continuous magnetic field around it. The receiver is also a winding coil on an iron core, but without a power source.

Depending on the intensity generated by the transmitter, the receiver can detect a magnetic field, generating an electric voltage at its edges. When there is metal between the transmitter and the receiver, this voltage changes – this is what we call magnetic flux deformation.

Detectors created to prevent the passage of weapons have a high sensitivity to this change. Then, when they detect metal, they trigger an alarm or close the turnstiles.

What kind of metal do they discover?

Ferrous and non-ferrous metals and stainless steels. Depending on the amount or type of metal, the change in magnetic flow lines may be greater or less. With this, you can calibrate the detector so that it responds to a greater or less impact on voltage.

Are metal detectors bad for your health?

It’s the same thing as using a cell phone, for example. Anyone who is constantly exposed to electromagnetic waves may experience headaches, but the World Health Organization (WHO) does not classify this as a disease. On the other hand, the International Agency for Research on Cancer classifies electromagnetic waves as one of the factors that promote the emergence of cancerous diseases. However, there is no consensus on this issue.

Do they warn against prosthetics?

Yes, as long as they are made of metal, this also applies to implants such as plates, pins and screws. But, depending on the detector, the size of the prosthesis can affect this. The recommendation is that people with prosthetics or implants notify the personnel responsible for safety.

Who can’t go through metal detectors?

People who have a pacemaker, which is a device with a battery-powered microcircuit. Electromagnetic signals from metal detectors can cause interference, prevent their operation and even modify their programming.

Those who use prosthetics with more advanced technologies, such as those that replace parts of the body and work using electrical signals, should avoid going through the devices, as they contain microelectronic devices and generate electronic signals. In these cases, electromagnetic waves may damage the operation process.