Metal Detector Operating Frequency: What It Is and Which Is Better to Choose

The most important criterion to consider when choosing a metal detector is the frequency. The operating frequency of a metal detector is the number of waves it emits per unit of time. These waves pass through the ground and bounce off metallic objects, and when detected, the metal detector emits a specific sound. The standard frequency range for industrial metal detectors usually varies between 3 and 100 kHz. The depths at which metals can be detected can vary significantly. This depends on the metal content in the soil, the size of the detected object, and the material it is made of.

Read Also : Multi-frequency metal detectors

Why and for what purpose do metal detectors operate at different frequencies?

Low-frequency devices (2.5-6.6 kHz) penetrate deep into the soil, but they are weak at detecting small objects. High-frequency metal detectors (20-100 kHz), on the other hand, are better at detecting small items such as coins and jewelry, but they operate either on the surface or at very shallow depths. Moreover, high-frequency detectors perform poorly in salty soil, although they are resistant to electromagnetic interference. Of course, you would want to have a metal detector that searches deeply and ideally distinguishes between all types of metals.

Metal Detector Operating Frequency: What It Is and Which Is Better to Choose

Operating frequencies of PI and VLF metal detectors

The operating principle of metal detectors is similar to the operating principle of VLF devices (very low frequencies, usually from 2 to 20 kHz) and PI devices (pulse induction, usually operating at frequencies above 22 kHz). The devices generate a pulse, then send it into the ground, and then receive a response. The response of the devices varies depending on the type of obstacle encountered.

The VLF metal detector consists of two coils. One transmits the signal, and the other receives and analyzes it. In pulse induction devices, one of the coils is responsible for generating and receiving the signal. The transmission and reception phases continuously alternate. Single-frequency metal detectors rely on single-frequency technology with continuous energy emission. A metal detector that focuses all its energy flow on a single frequency distinguishes metals better and allows for deeper detection. Single-frequency detectors are more resistant to external interference, operate more efficiently, and consume less battery power. Metal detectors such as the Bounty Hunter Gold, Garrett ACE 250, Garrett ACE, Teknetics Eurotek, Minelab Go-Find 22, and Whites Coinmaster operate at a frequency of approximately 6 to 8 kHz and are versatile. They can detect small coins at a depth of about 20 to 25 cm and helmets and samovars at approximately 80 cm. Larger items, such as tanks, can be detected at a depth of up to one and a half meters.

For gold and coin prospecting, high-frequency devices with a range between 20 and 100 kHz are used. Experienced prospectors recommend searching with two devices. First, search the area with a low-frequency metal detector, then with a high-frequency one. However, in soils with high mineral content or in salty water, their performance drops significantly, almost by half.

Multi-frequency Metal Detectors

Multi-frequency metal detectors include the following types of devices:Working simultaneously across multiple ranges.Switching using a switch from one frequency to another.Changing the search frequency by replacing the coil.Although they save a lot of time and increase the number of finds, these devices are weak in distinguishing between metals and are the most expensive among all metal detectors. While multi-frequency detectors suit experienced treasure hunters, they may present a challenge for beginners.

Metal Detectors with Switchable Frequencies

One of these metal detectors is the Golden Mask 4WD device. The frequency is switched with a toggle switch from 8 to 18 kHz.The Minelab X-Terra Pro is a multi-frequency device. You can switch between four operating frequencies - 5, 8, 10, and 15 kHz - with a button on the control panel. You can search using any of them, depending on your goal.These metal detectors have many advantages, including high-precision gold discrimination and deep detection. The XP DEUS series provides up to 5 operating ranges and allows searching the ground up to a depth of 35 cm.Well-known metal detectors, also known as "Aka," change frequencies by replacing the coil. They are available in two versions: dual-frequency and triple-frequency (the desired frequency is selected using a switch).

Metal detectors with a range of frequencies (harmonics)

Metal detectors with harmonics emit full frequency ranges during the generated pulse, with an infinite number of variations. Their high sensitivity to external interference can cause false alarms.You should not assume that if a metal detector works with 28 frequencies, it is equivalent in search performance to 28 detectors.

Metal detectors that operate at multiple frequencies simultaneously

These devices include the Minelab Excalibur II, Etrac, and CTX 3030. Multi-frequency metal detectors, ranging from 1.5 kHz to 100 kHz, provide greater versatility. With up to 30 frequency bands, these devices allow you to easily detect small items such as coins and jewelry, as well as search in saltwater or on the beach. Their operation is not affected by highly saline soil.

Read Also : The main types of metal detectors

Minelab Equinox devices operate on multiple frequencies simultaneously. All metal detectors are capable of easily searching in water at depths of up to 3 meters. The EQUINOX 800 and 900 devices have six frequencies, ranging from 4 to 40 kHz. You can search either in multi-mode or single-frequency mode. The Equinox 600 and 700 devices operate in the same range but with lower single frequencies (from 4 to 15 kHz).

However, the prices of these devices are already in the six-figure range and are not always within reach for beginners and casual hobbyists.

The search process is complicated by excessive sensitivity to small aluminum pieces, metal flakes, and other metal debris, which are abundant near populated areas. Therefore, these devices are suitable for professional gold prospecting in mining sites and geological exploration.

Read more about: metal detectors operating principles

What operating frequency should I choose?

When selecting a metal detector, you should realistically assess your experience, goals, and budget. Beginners are recommended to use a device with a universal frequency of around 7 kHz. This is suitable for searching for jewelry, coins, and relics. A high-frequency metal detector is very helpful when searching for raw gold pieces. As for experts in the field of detecting, they can easily handle a multi-frequency metal detector. Depending on the soil when choosing the appropriate metal detector, it is important to consider the type of soil you will be searching in. Avoid scanning deep rocky formations, as you won't be able to dig them manually anyway. In dry areas with low soil moisture, even a mid-range metal detector will perform poorly. In these cases, it is better to postpone the search until the wet autumn or early spring. For searching on beaches and even in water, you will need a metal detector with a waterproof cover. Pulse detectors work best in high-mineral soils because they do not require continuous adjustment.

Depending on the purpose of the research

If you clearly define your research goal and do not try to cover everything at once, you can choose your device based on its specifications.

For searching for jewelry, coins, and other small items, you will need a metal detector with good selective discrimination capability. The search area is usually heavily contaminated with conductive metal debris, so it is preferable to filter out finds that are not worth your effort and attention immediately. The Garrett AT Pro, also known as "Proshka" by detection experts, is a mid-priced device. The Nokta Makro Simplex is also suitable for this type of search, as it is easy to use and highly sensitive.

Read Also : Best Frequency for Detecting Gold

Finding artifacts and military items requires detectors with a frequency of approximately 12 to 15 kHz and good discrimination. Garrett's ACE Apex and AT Max meet these requirements. They are characterized by reasonable prices, easy setup, and high sensitivity in all types of soil.

To search for gold pieces, you need a metal detector with a frequency of 20 kHz or higher. The XP ORX metal detector is easy to use, reasonably priced, and detects both gold pieces and jewelry. Detecting beaches and coastal waters requires good water resistance and high mineralization resistance. These metal detectors are much more expensive than ground detectors. The Nokta Makro Anfibio Multi and Minelab Equinox 800 are considered affordable in their category. The latter is also excellent for land detection, as it is a versatile device suitable for any soil type or target.

Proposed topics for you :

There are many metal detectors available to choose from, and it can be difficult to select just one. To narrow down your options, you should ask yourself a few questions. Do you have enough experience in searching for underground treasures, or are you just starting in this exciting field? What terrain do you plan to search in, and what is the nature of its soil, and its moisture level? What are you looking for – artifacts, relics of war, iron metals, or gold? How familiar are you with the device's control tools?

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