How Metal Detectors Work

Anatomy of a Metal Detector

Garrett GTI 1500 metal detector
Garrett GTI 1500 metal detector
Photo courtesy Garrett Electronics

A typical metal detector is light-weight and consists of just a few parts:

  1. Stabilizer (optional) - used to keep the unit steady as you sweep it back and forth
  2. Control box - contains the circuitry, controls, speaker, batteries and the microprocessor
  3. Shaft - connects the control box and the coil; often adjustable so you can set it at a comfortable level for your height
  4. Search coil - the part that actually senses the metal; also known as the "search head," "loop" or "antenna"

Most systems also have a jack for connecting headphones, and some have the control box below the shaft and a small display unit above.

Operating a metal detector is simple. Once you turn the unit on, you move slowly over the area you wish to search. In most cases, you sweep the coil (search head) back and forth over the ground in front of you. When you pass it over a target object, an audible signal occurs. More advanced metal detectors provide displays that pinpoint the type of metal it has detected and how deep in the ground the target object is located.

Metal detectors use one of three technologies:

  • Very low frequency (VLF)
  • Pulse induction (PI)
  • Beat-frequency oscillation (BFO)

In the following sections, we will look at each of these technologies in detail to see how they work.