What “Frequency” means

What does frequency mean when metal detecting?

A common definition of frequency is as follows: The number of waves per unit of time measured in kHz or kiloHertz.  In a metal detector this is the number of electronic waves sent into the ground to detect metal.

Example: 10 kHz means your detector will send and receive 10 000 times per second.

Why is Frequency important?

  • Both Pulse induction and beat frequency oscillator (VLF) type metal detectors use frequency of electronic fields or pulses sent into the ground.
  • Different frequencies have different advantages and disadvantages when metal detecting.
  • Metal detector frequencies range between 3 – 100 kHz as a general rule.

Low Frequency.

  • Have longer wavelength.
  • Gets greater depth as long waves penetrate the ground more easily.
  • Better for detecting high conductivity targets like silver.
  • Not good for finding smaller targets.
  • Not good for low conductivity targets like gold or Iron.

High Frequency.

  • Have shorter wavelengths.
  • Great for detecting small objects like tiny gold nuggets.
  • Better for low conductivity targets like gold and Iron.
  • Less depth is achieved than low frequency.
  • Higher accuracy, closer to the surface.
  • More sensitive to ground mineralisation

Most hobby detectors use a middle ground to try and get the best of both frequencies in the Goldilocks zone around 6 – 8 kHz for the best depth and sensitivity trade off. Some detectors even let you manually set the frequency on your detector.  Others even use multiple frequencies at one time.

Frequency and Conductivity.

Metal objects in the ground all conduct electricity better or worse. This may be plotted on a scale from Ferrous iron on the low side to Non Ferrous silver on the high side with gold and foil somewhere in the middle. This is often the basis for the LCD screen layout.

Hobby metal detectors can tell the type of metal by how well it conducts electricity of the frequency pulses it sends into the ground (usually the speed that the signal sent back decays over time.) This allows the modern hobby metal detector to discriminate between metals and not only indicate the type of metal it thinks it’s found but also allows you to screen out certain metals like iron if you want to stop the detector from picking them up.

We hope this helps your choice and understanding of a hobby metal detector and frequency!

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