Metal Detectors

Metal Detectors: Technologies, Uses, and Considerations

Metal detectors are invaluable tools for locating buried or concealed metallic objects. Advanced detection capabilities allow discovering treasure, maintaining security, avoiding underground hazards, and more. Understanding metal detector technologies and applications allows selecting the right detector for the task.

Metal Detector Technologies

Metal detectors rely on electromagnetic fields to detect disturbances caused by metal. The main technologies include:

• Beat Frequency Oscillation (BFO) - Two oscillating coils running at slightly different frequencies produce an audible tone when metal disrupts the fields. Affordable but less sensitive.
• Pulse Induction (PI) - PI detectors send out magnetic pulses then listen for feedback. Highly sensitive and minimally affected by mineralization but with limited target discrimination.
• Very Low Frequency (VLF) - VLF detectors transmit a continuous sine wave signal from the search coil. Disruptions allow identifying different metals. Provides excellent discrimination.

Selecting the right technology involves tradeoffs between sensitivity, discrimination, depth, and cost to match needs.

Security and Safety Applications

Metal detectors enhance security and safety in various environments:

• Airport Security - Scan passengers for prohibited items like guns, knives, and explosives.
• Loss Prevention - Detect shoplifted merchandise concealed in bags or clothing.
• Public Buildings and Events - Screen visitors at government offices, stadiums, music venues, and rallies.
• Prisons - Find hidden weapons and contraband during cell searches.
• Schools - Deter students from bringing weapons into schools.
• Worksites - Tool detectors prevent unauthorized tools entering high security areas.

Advanced detectors can discriminate and identify different metals and alloys.

Industrial and Commercial Uses

Metal detectors play an important role in manufacturing and business:

• Food Processing - Detect and remove metal contaminants from food products.
• Textiles - Identify broken needles in fabric and remove them.
• Packaging - Verify packaged products are metal-free before shipping.
• Recycling - Sort scrap metal types during recycling.
• Construction - Locate rebar, conduit, and other buried metal before excavating.
• Mining - Identify ore types based on conductivity signatures.

Specialized detectors are designed for unique industrial purposes.

Archaeology, Treasure Hunting, and Hobbyist Use

Detector enthusiasts take advantage of advanced technology to uncover buried items:

• Coins and Jewelry - Unearth old coins, rings, and necklaces from yards and beaches.
• Relics - Discover artifacts and militaria from historical battlefields and sites.
• Meteorites - Locate naturally occurring metal space debris that survives impact.
• Gold Prospecting - Pinpoint gold nuggets based on unique conductivity signatures.
• Underwater Detecting - Special waterproof detectors work for shallow freshwater finds.

Researching local history provides clues on potential detecting sites.

Considerations When Selecting and Using Metal Detectors

Key factors to consider when purchasing and operating metal detectors include:

• Frequency - Low (VLF), mid-range (PI), or high-frequency capabilities based on detection needs.
• Search Coil Size - Larger coils offer wider detection swaths while compact coils provide more detail.
• Detection Depth - Maximum depth range needed - shallow surface or deep detection.
• Discrimination - Ability to identify specific metals versus a generic signal for all metals.
• Environment - Intended use environment such as soil conditions, temperature extremes, and moisture.
• Battery Life - Hours of use per charge based on rechargeable versus disposable batteries.

Carefully reading specifications allows matching the detector to intended applications.

Proper Metal Detector Use Techniques

For successful detecting, utilize proper techniques:

• Conduct test sweeps over known targets to adjust settings and practice technique.
• Walk slowly and methodically holding the coil 2-4 inches above and parallel to the ground.
• Overlap sweeps in a grid-like pattern to ensure full coverage.
• Dig carefully once a target is isolated - use small hand tools to avoid damaging items.
• Refill all holes and leave the area as it was found after recovering an item.

Patience and practice lead to honing metal detection skills.

Todays advanced metal detectors open new possibilities for security teams, businesses, archaeologists, prospectors, and hobbyists. Applied properly, detectors greatly increase the odds of unearthing unique treasures or maintaining safer, more productive environments. By understanding the technology and techniques behind metal detection, you can leverage these invaluable tools to their fullest potential.