Metal detectors are the best way to find lost treasure, but not all metal detectors are built with the same power. We’re going to go over the different types of metal detectors, and how deep they detect.
How Deep do Metal Detectors Detect?
The average metal detector with a basic coil can detect things 4-16 inches down, the average being around 8 inches deep. A metal detector with a small coil has less power than a larger professional coil. A pulse induction metal detector penetrates the ground, giving you a deeper depth, of up to 65 inches.
There are a few different types of metal detectors, each one has advantages and disadvantages for depth. Let’s look at the different types, so you can find the right one for you. To see how metal detectors work, check out our post here.
Types of Metal Detectors and Their Depths
There are three main types of Metal Detectors. One is for beginners, and the other two are for those who are serious about metal detecting. There are other more specialized types of metal detectors as well, which we will go over later in the article.
The BFO metal detector is one of the first designs. These are used today for toy models and beginner metal detectors. These detectors are not ideal for a serious treasure hunter. Newer technology allows much deeper depths.
Very Low Frequency
VLF metal detectors are one of the most common metal detectors. These use a low frequency to locate items. I have found personally that VLF detectors are better at finding larger items. The lower the frequency finds large items, while a higher frequency gives you more sensitivity to find small coins and items. As far as depth, the VLF models can find relics at deeper depths, if they are large relics.
PI metal detectors send a pulse through the ground, this pulse can penetrate deeper into the ground than the other two types. With a good PI metal detector, you can find items 3 feet deep or more. This gives it a huge advantage over the other two.
There are many more things to consider when dealing with depth. The mineralization of the soil, the size of the coil, and the technology, your type of metal detector uses can all play a part in the overall depth. Even the shape of the item you are detecting can come into play.
What is Soil Mineralization?
The area where you are using your metal detector can make a big difference in how well your detector works, for depth, and other factors. Soil mineralization is something that refers to how magnetic the ground is.
New soils, that are created by natural processes, such as erosion and glacial scraping have less mineralization. Very old land has soil that has been on the surface for a long time. This dirt has more iron in it, from years of rain.
Red soil is a sign that it has more mineralization. The red color is from the amount of iron in the soil. The problem with mineralized soil is that it creates a magnetic response from your metal detector.
This can cause a loss of depth in your metal detector. Some metal detectors have technologies that can read the mineral content, such as ground balancing and ground tracking.
Size Matters Coil Size and Target Size
How deep metal detectors go, has to do in part, with the size of the coil, and the target size of the object. A larger coil will be able to find large items deep in the ground, while a smaller coil will be able to home in on smaller targets, such as small coins and pieces of gold. Source.
Most metal detectors allow you to switch out coils. You may want to have more than one size coil, depending on what your goal is for your particular project. For example, if you are looking for large relics, a larger coil will work better. If you are looking for small pieces of gold, a smaller coil is better.
The shape of the coil also matters. Round coils are the most common, and they are the best for depth. Ecliptical coils, on the other hand, allow you to cover more area, but less depth.
Metal Detector Frequencies
Frequency is the next factor for how deep can a metal detector detect. The frequency of a metal detector has to do with the number of electronic waves that are sent into the ground.
Low frequency, such as 8kHz or lower, is good for finding larger items, or more conductive targets like silver and copper. VLF and low-frequency detectors, send out longer electronic waves. This makes it easier to find large items, deeper down.
Higher frequency detectors, such as 40kHz, can find smaller items and less conductive metals, such as stainless steel. Since you may be wanting to find deeper items and small items, you may want to go with a multi-frequency metal detector, these give you more to work with.
Metal Detection Software
All metal detectors come with different types of software. Some have more bells and whistles than others and offer more control over sensitivity, and discrimination on deeper items.
One thing, metal detectors with better software have is ground balancing and ground tracking. Ground balancing/tracking increases your direction depth in mineralized soil.
Software that has better discrimination, can help you avoid items like nails and bottle caps, by setting the discrimination to avoid them. This lets you find items below those items, at a deeper depth.
Metal Detector Sensitivity
When you set your sensitivity, you are doing two things, you are increasing the transmitting power, and you are homing in on specific types and sizes of metals. Some believe that the more sensitivity you have, the more depth you can detect.
This means with more sensitivity, you have a better chance of finding small items, at a deeper depth.
Pairing this with discrimination means you can find much smaller items deeper down, without surface items, like screws, throwing you off. This can be very helpful for finding old coins, that have been buried deeper with time.
Specialized Metal Detectors for Depth
The three main types of metal detectors mentioned at the beginning of this article are not the only types on the market. There is always newer technology being produced, that has more power for depth.
Sometimes you may need something more specialized. These types of metal detectors are more expensive and are only for the serious treasure hunter who needs this type of technology.
Multi-Frequency Metal Detectors
Multi-frequency metal detectors may cost a little bit more, but they give you so much more variety when searching for metals. Low-frequency (VLF) metal detectors, typically work better for finding larger items. Being able to switch between low and high frequencies, allow you to set your detector for different sized objects.
Two-Box Metal Detectors
If you are searching for much deeper items. The two-box metal detectors are the best on the market. These are used to find large caches and relics deep down in the ground. Your typical metal detector uses one coil, while two-box detectors use a pair of rectangular sear coils. However, these detectors are for items that are 3 feet and lower.
A magnetic locator is a specialized metal detector that is used to find large iron and steel items. They can be used to find cast iron pipes, property markers, and deeply buried iron items. These are used mainly by construction companies.
How Deep Underwater Can a Metal Detector Detect?
Underwater metal detectors are also specialized metal detectors, in that they are designed for detecting underwater. Many non-specialized metal detectors can detect underwater, up to a certain point. However, they usually cannot be fully submerged.
Metal detectors that are fully submersible, and not just waterproof, can be very costly. If you are not using it to be fully submersible, then a regular waterproof one could be right for you. These are ones that the coil can be submerged in water but the control box cannot.
A fully submersible metal detector is used for diving. Many treasure hunters dive deep down to find things like shipwrecks and old coins. In this case, you can expect a fully submersible metal detector to be able to detect 200 feet below, sometimes deeper.
There comes a time in every rightly constructed boy’s life when he has a raging desire to go somewhere and dig for hidden treasure.Mark Twain
Will a metal detector find buried electrical wire?
Depending on the type of metal detector and how deep the wire is, yes they can find buried electrical wire. If it is buried more than 3 feet down, you may need a specialized metal detector such as a magnetic locator.
What metals cannot be detected by a metal detector?
Metals that have low conduction cannot be found as easily with a metal detector. Also, very small pieces of low conduction metals are much harder to pick up on a metal detector.