How Do VLF Metal Detectors Work

by Michael Bernzweig

So, which is the best metal detector for you? It depends on what you're looking for and where you'll use it. There are two main types of circuit technologies used today VLF, Very Low Frequency, and PI, Pulse Induction. This article will explore the differences between these two kinds of detectors, how they work, and what they're best used for. A VLF metal detector is your best bet for raw gold prospecting or precious metal hunting. A VLF machine operates between 3 and 30 or kHz or higher. It is also an excellent option for coin, jewelry, or relic hunting. This kind of detector is generally less expensive than its Pulse Induction counterpart because the technology is more popular and in higher production. The higher the frequency, the more apt your VLF detector can function as a gold metal detector. This type of unit is ideal for gold nugget hunting. Lower frequency models are better for locating iron and other ferrous metals. Mid frequencies are typically the best for locating an individual coin and other common targets like relics and jewelry. For this reason, a VLF multi frequency detector model is a great option for covering all of your bases. This type of VLF detector sends out signals across multiple frequencies simultaneously.

VLF metal detectors send out a low-frequency signal that is then reflected back to the detector when it comes into contact with metal. The strength of the signal depends on the type of metal and its conductivity.

VLF machines are good at detecting a small metal object and are excellent for distinguishing between different types of metals as you metal detect. A search coil on a very low frequency or VLF detector emits a low-frequency electromagnetic field into the ground. Eddy current responses are then used to determine the presence of metals. When this field comes into contact with metal, it creates a secondary field that's picked up by the coil. This signal is then amplified and sent to the control box, where the user interprets it. The signal response may be presented in a number of ways such as one or a combination of the following methods:

  • An Audio Tone
  • Multi Tone Audio
  • Visual Identification, such as on an LCD screen
  • Vibration, ie hand grip of the detector or bone conductor headphone while diving

VLF Metal Detector Applications

VLF detectors are better for gold prospecting in many conditions and can detect gold nuggets and underground gold deposits. VLF detectors are also good for finding coins, jewelry, and other small metal objects. With Target ID, these detectors can also help you identify the type of metal you've found.

Gold metal detectors that operate on the lower end of the frequency spectrum are less likely to be affected by hot rocks and highly mineralized soils, which can cause false readings on higher frequency machines.

This type of detector is also generally lighter and easier to use than a pulse induction model, making it a good choice for beginner treasure hunters. However, VLF detectors can have difficulty penetrating deep into the ground, so they're not always the best choice for looking for objects buried many feet or meters underground. Fisher metal detectors produce the F75 metal detector, which is a great all-around coin relic and jewelry metal detector featuring single frequency VLF detection. The XP DEUS 2 would be an example of a Fast Multi Frequency VLF metal detector that operates across various VLF frequencies.

What are Pulse Induction Metal Detectors, and How Do They Work?

Pulse induction metal detectors emit short pulses of electricity that penetrate the ground. These pulses create a magnetic field that attracts metal objects. The detector then measures the magnetic field's strength to determine the object's location.

Pulse induction or PI metal detector sends out short pulses of electricity and then measures the time it takes for the pulses to bounce back. This method is very effective at finding large pieces of metal, but it can have trouble detecting smaller pieces.

A PI detector is also less likely to be affected by ground mineralization. Pulse Induction (PI) works better in highly mineralized soil and saltwater. The Garrett ATX is one of three PI models from Garrett and one of the best metal detectors for gold nugget prospecting and beach hunting. The Garrett ATX features manual and automatic ground balance and is waterproof up to 3 meters.

The feature of ground balancing is important because it cancels out the natural minerals in the ground that can interfere with your detector's ability to find metal objects.

Detech metal detectors and Garrett metal detectors are two brands that also offer pulse induction models. The Detech 5100 Pro is a top unit for locating large deep buried treasures. The Garrett Axiom is a professional gold prospecting model with extreme sensitivity to small gold nuggets.

Pulse Induction Metal Detector Applications

Precious metals detection is one of the main applications for pulse induction detectors. This is because they can penetrate deep into the ground and find large pieces of metal that other detectors with a lower maximum depth detection would miss. They're also good for finding objects in saltwater or highly mineralized soil.

Metal objects like iron relics, gold nuggets, and silver coins are all detectable with a pulse induction machine. However, because these detectors don't discriminate between different types of metal, they're not always the best choice for finding small objects like coins or jewelry.

Differences Between VLF Metal Detectors & Pulse Induction Metal Detectors

Pulse induction metal detectors are better for finding deep, buried objects. They're also less affected by highly mineralized soils, which can interfere with VLF detectors' preset ground balance. VLF detectors excel at finding small, shallow objects. They're also easier to use and generally more affordable than pulse induction models. If you are searching for larger or deeper objects or large veins of raw gold, a pulse induction treasure detector may be your best bet. While a VLF treasure detector will locate targets, it can also provide the most accurate target identification.

Metal detecting is a great hobby that people of all ages can enjoy, but before you can start exploring, you need to find the right metal detector. VLF and PI detectors both have their own strengths and weaknesses, so it's important to choose the right one for your needs.

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