If you are on the hunt for buried treasure, a metal detector is your best friend. With this amazing device in hand, you never have to guess about where to dig. You just wait for the detector to tell you it has struck gold (or some type of metal, at any rate)!
But how does a metal detector work on a scientific level, and what are all of its capabilities? In this article, we’ll give you the rundown on the technology, frequencies, tips for use, how to shop for metal detectors, and more.
Understanding How Metal Detecting Technology Works
A metal detector works through the application of a magnetic field.
Here is what takes place in simple terms when you are using your metal detector:
- You turn on the metal detector, and generate a transmit signal using the control box.
- In response to your action, the search coil on the metal detector generates a magnetic field through the power of electricity. The search coil may also be referred to as the “search head,” the “antenna,” or the “loop.”
- As you walk around, that magnetic field penetrates the ground.
- Let’s say that while you are walking, the metal detector passes over a metal object which is hidden underground.
- The meeting of the magnetic field and the metal item results in alternating voltages of electricity flowing through the metal. This alters the magnetic field.
- The receiver coil on the metal detector picks up on this change.
- A cable routes the observations which the receiver coil detected up to the control box.
- The control box produces one or more cues for you. There is usually an audio beep or buzz, and sometimes there is also a needle that moves. This depends on the model of metal detector which you purchase.
- You may have found a treasure. It’s time to get out your shovel and start digging!
That is the most basic explanation for how a metal detector works.
You can of course read far more in-depth scientific explanations concerning what goes on with the magnetic fields and electricity, but suffice to say, it is an elegant device which gets the job done.
Key Point: A metal detector works by sending a magnetic field into the ground to interact with and be modified by a metal object. It then detects those alterations in the field and alerts you to the presence of an object.
Metal Detector Frequencies
One of the main features of metal detectors is the frequencies they work at. This should be among your prime buying considerations when you are selecting a model to purchase.
Frequencies can range from around 3 Khz to as much as 100 Khz.
When to Choose a Low Frequency Metal Detector
You want a low frequency metal detector when you are interested in finding:
- Large objects.
- Objects which are buried deeply.
- Objects which are highly conductive (certain metals fit into this category, a prime example being silver).
When to Choose a High Frequency Metal Detector
Think about getting a high frequency metal detector when you are interested in finding:
- Small objects.
- Objects which are not buried as deep.
- Items that are made out of metals that are less conductive, i.e. iron or gold.
Other Frequency Considerations
While what you are searching for will probably be the largest factor in determining what frequency to use, you also should think about your environment.
Different types of soil have different mineralization statuses. If soil is “mineralized,” it behaves like metal in response to the field your device is generating.
The soil you are thinking about searching for metal objects may be highly mineralized if:
- The soil is old
- The soil is in an area which receives a lot of rainfall
- The soil has a reddish color
Low frequency metal detectors usually do a pretty good job handling this type of interference, but high frequency detectors do not.
This can put you in a quandary. Say, for example, that you want to search for gold. Unfortunately, this may take you to a vicinity which features the exact type of soil conditions that can falsely trigger your high frequency metal detector.
Thankfully, there are metal detectors which are built specifically to help filter out such unwanted interference while you are searching for gold.
What if you want to make use of both high and low frequencies for different applications?
If that is the case, you can shop for a metal detector which includes dual or multiple frequencies.
Key Point: The frequency of a metal detector determines the applications which it will be most effective for. Decide whether to purchase a low frequency, high frequency, or multiple frequency metal detector based on what you want to search for. Take your location and the nature of the soil into account as well.
How to Shop for a Metal Detector: Key Features to Look For
We have talked about frequencies of metal detectors. But there are other features which also need to be considered when you are choosing a metal detector to use.
- Ground balance: Remember how we talked about filtering out interference from soil mineralization? This feature is referred to as “ground balance.” Metal detectors that are equipped with this technology may have a preset, or may allow for manual adjustments. Still others may be able to automatically adjust themselves on the fly as you move through different environments.
- Target identification and discrimination: Some metal detectors can tell one type of object from another. With these features, you are less likely to waste time digging for junk.
- Sensitivity: This literally refers to how sensitive a particular metal detector is. It could be fixed or adjustable setting.
- Depth: As discussed, this is related to frequency. If you want to maximize the depth that you can search with your metal detector, a low frequency model with a large coil is ideal.
Meta Detector FAQ
Q: How deep can my metal detector detect?
A: The size of the coil and the frequency will determine the depth, all environmental factors being equal. Technology such as pulse induction also can enhance depth.
That being said, the nature of the soil as well as the features and even the orientation of the object being detected will also factor in.
Smaller objects become harder to detect than larger ones at a greater depth. The more surface area that an item presents, the better. So if a coin is situated face-up, you may have an easier time detecting it at a certain depth than one nearby which is situated edge-up. The less conductive an object is, the harder it is to detect.
The majority of metal detectors on the market can search at a range somewhere between 20–50cm.
Most of the types of objects you are likely to be looking for not going to be any deeper than 7 to 90 cm underground.
Certain types of objects tend to be closer to the surface than others. So once again, what you are hunting for in the ground should inform your buying choice in this regard.
Q: How is a metal detector powered?
A: A metal detector is powered by batteries. The exact length of time those batteries last depends on the metal detector you buy. Usually you can opt for disposable or rechargeable batteries, usually either NiCads or Alkalines. You might get anywhere from 8-30 hours of use out of them at a charge, depending on the batteries you buy.
Q: Why do people wear headphones when using a metal detector?
A: In a loud location, it is pretty hard to hear the tones unless you have these. If you are metal detecting on the beach, for instance, with the roar of the sea right beside you, they are vital.
Q: Can I use a metal detector wherever I want?
A: No. You must look up the regulations and rules for any property where you are going to be searching. You can search in some spots and not in others.
Metal Detecting Tips for Newbies
Having answered some frequently asked questions about metal detectors, let’s go over some quick tips for beginners!
- Be realistic starting out. It is important to be aware that you need a lot of patience with metal detecting. The vast majority of what you find will be trash, even if you are searching in an area that has promise. Be prepared to do a lot of digging (literally) to unearth treasures.
- Do your research before you head out with your metal detector. If you just head to a random location and start searching, chances are good that you’ll come up with nothing to get excited about. But if you can pinpoint a destination by conducting research online and even consulting local sources (i.e. the city hall or local visitor’s center), you can start out your search in the right place.
- Don’t leave trash lying around. Seriously, collect it. Throw it in the recycling bin when you’re done. You’ll be doing your part for the environment.
- Choose isolated locations and quiet times of day. For whatever reason, passersby seem to be fascinated by people who are using metal detectors. If you choose a crowded spot to look for items, you can expect to get a lot of people staring at you, or even potentially walking up to you and starting unwarranted conversations.
- Be deliberate and measured with your movements. Do not leave gaps between your sweeps (a degree of overlap can be helpful in preventing this). Also make sure that you’re not sweeping in an upward arc away from the ground. Keep the metal detector level.
- When items are dropped or discarded, it is often several at a time. That means that finding one exciting item is a sign that you should take the occasion to look for more in your immediate surroundings. Whoever lost or threw away one coin or jewelry item may have dropped others.
- Wet soil is more conductive than dry soil. As a result, the depth which you can detect at increases following rain. Get out there and take advantage of those wet conditions when you can.
- Before you make use of discrimination settings on a metal detector, you should conduct some controlled tests to find out which settings are best for the types of objects you want to locate. Even though this should be straightforward, the reality is that there is a significant level of variation in performance from one device to the next. You may as well remove the guesswork in selecting your settings.
- A good place to learn how to use your metal detector is the beach (preferably when it is not crowded). The beach presents multiple advantages. First of all, some of the sand is wet and conducts well. Secondly, the beach receives a lot of foot traffic and lost items. Thirdly, the ocean current itself regularly brings in additional objects you can search for.
- Do not just randomly mill about an area in search of metal objects. Sweep it in an organized, methodical fashion. This takes patience, but it ultimately will save you time and effort—and you will not leave worrying that you might’ve missed something in your search area.
- Along with a bag to collect whatever you find, you should also bring a notepad with you or maintain a document on your mobile device. Whenever you find something noteworthy, take down the exact location (including coordinates if you have them). Over time, the information you collect will help you to better target future outings with your metal detector.
What Is The Best Metal Detector For Beginners?
You can read about our current obsession with the MineLab Equinox 800 here to see why it is newbie friendly.