How Metal Detectors Work

Buried Treasure

Metal detectors are great for finding buried objects. But typically, the object must be within a foot or so of the surface for the detector to find it. Most detectors have a normal maximum depth somewhere between 8 and 12 inches (20 and 30 centimeters). The exact depth varies based on a number of factors:

  • The type of metal detector - The technology used for detection is a major factor in the capability of the detector. Also, there are variations and additional features that differentiate detectors that use the same technology. For example, some VLF detectors use higher frequencies than others, while some provide larger or smaller coils. Plus, the sensor and amplification technology can vary between manufacturers and even between models offered by the same manufacturer.
  • The type of metal in the object - Some metals, such as iron, create stronger magnetic fields than others.
  • The size of the object - A dime is much harder to detect at deep levels than a quarter.
  • The makeup of the soil - Certain minerals are natural conductors and can seriously interfere with the metal detector.
  • The object's halo - When certain types of metal objects have been in the ground for a long time, they can actually increase the conductivity of the soil around them.
  • Interference from other objects - This can be items in the ground, such as pipes or cables, or items above ground, like power lines.

Hobbyist metal detecting is a fascinating world with several sub-groups. Here are some of the more popular activities:

  • Coin shooting - looking for coins after a major event, such as a ball game or concert, or just searching for old coins in general
  • Prospecting - searching for valuable metals, such as gold nuggets
  • Relic hunting - searching for items of historical value, such as weapons used in the U.S. Civil War
  • Treasure hunting - researching and trying to find caches of gold, silver or anything else rumored to have been hidden somewhere

Many metal-detector enthusiasts join local or national clubs that provide tips and tricks for hunting. Some of these clubs even sponsor organized treasure hunts or other outings for their members. Check out for more information on clubs.