Metal Detectors

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With your trusted metal detector in hand, you walk down the beach. The sun is setting pleasantly on the horizon and you're wondering if you should just call it a day. You've been out with friends all day without much success in finding anything promising. Your heart always seems to beat a little faster when you're on the hunt, and suddenly, the familiar noise is heard: time to start digging! There is great thrill in the search, so much in the world to be found and rediscovered. These treasures want to be found, they want to be discovered, and you want to be the one to discover them.

How do you use a metal detector?

Always check with the manufacturer for directions on using individual detectors. In general, here are things to know when using a metal detector:

  • Practice patience and break your search area into grids.
  • Practice sweeping slow and low to the ground.
  • Become familiar with sounds and tones.
  • Mark your spot and bury a coin to help you return to it.
  • Test your detector on different metals you bury underground to see if it locates each one.

What types of metal detectors are there

Common metal detectors include:

  • Beat frequency oscillator (BFO): Typically preferred by beginners, these are the least expensive detectors. They use radio waves and magnetic fields to detect metal. While they are helpful for the casual hobbyist, they are the least effective tools to locate precious metals. They locate all metal materials and cannot differentiate one from another.
  • Very low frequency (VLF): These detectors use a very low-frequency signal with electromagnetic fields to locate metal underground. These metal detectors also have phase shift knobs. VLF detectors are also called discrimination detectors because they discriminate between items made of steel and those containing gold or silver.
  • Pulse induction (PI): Serious treasure hunters prefer these detectors. They are the least common and the more expensive of the three types. They use magnetic pulses to locate buried metals instead of radio frequencies. This allows deeper penetration into the ground and can be used in salt water where radio frequency detectors do not work.

How do different types of metal detectors locate items?

Two of them use radio frequencies and one uses magnetic pulses, all with varying degrees of success. Here is a basic breakdown as to how each works:

  • BFO: This type of detector contains two coils. One is in the control box, and the search head contains the other coil. An oscillator runs between the two coils. Using a fixed frequency, it generates radio waves. If the search coil locates metal, it disrupts the connection to the oscillator. That interrupts the radio frequency, letting you know it found metal.
  • VLF: Using two coils, the outer one sends a very low-frequency signal toward the ground. This transmitter locates metals underground using electromagnetic signals. When it does, it sends up an audio signal to the receiver coil. Upon hearing this audio tone, you turn a knob called a phase shift. It lets you know if the metal falls within a certain group like gold, silver, or steel.
  • PI: Sending pulses of current rapidly through a coil, PI technology relies on each pulse to generate a magnetic field that reverses polarity to collapse very suddenly. This happens somewhere between 100 and 1,000 times per second. A sharp electrical spike generates reflected pulses likened to an echo. When it hits metal, the reflected pulse creates a much longer echo to let you know it found a metallic object.