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Metal Detector Glossary - a guide to specialized terms

Metal Detector Glossary - a guide to specialized terms

The world of metal detecting is a highly specialized activity. Whether you're using one of the best metal detectors to plan out a redesign of your garden, to search for metal around your home or business, or to just hunt down coins and trinkets in your spare time, it pays to know the terminology. You'll find a number of excellent forums and discussion threads around metal detection, as there is a large community, and they will all be using specific phrases to discuss their activity. We've rounded up the most common phrases below.

While our list of metal detection terms is far from exhaustive, these are the things you're most likely to see. Many are technical aspects of the devices themselves, but some are just terms used by enthusiasts. If you're detecting metal as part of a garden project, make sure you check out our guide to the best landscape design software. If it's more of a hobby, good luck finding those trinkets!

Metal Detector Glossary

Coinshooting

Many hunters will use a detectors' discrimination and target ID functions to filter out trash (and the gold that gets confused for trash) in order to concentrate on collecting coins, which they'll then clean, keep, sell, or use to buy a drink after a long day of coinshooting.

 Detection Depth

You would think detection depth would be the most important factor to consider when picking a metal detector, but it's not. The truth is that it's always an estimate and there's no good test manufacturers can run to pin it down. A slew of factors contribute to a detector's depth range, from the size and shape of its coil to the composition of the ground you happen to be scanning. 

You can air test a detector by passing coins in front of it at various distances something enthusiasts do all the time   but it's not a true reflection of real-world use. A device might detect coins beneath 11-inches of soil in one region, and not find the same coin under just seven-inches of soil in another. In general, don't expect to reliably find treasures more than ten-inches deep with any detector, unless they're particularly large pieces of metal. 

Even then, they tend to confuse detectors and give spotty readings. If you're lucky enough to find a treasure chest filled with Spanish doubloons buried three feet down, it will probably read as anything but gold on your target ID until you excavate it.

Discrimination and Notching

Discrimination is a detector's ability to exclude certain objects, usually trash, to make it easier to find other metals. Since metal detectors spot objects based on their conductivity, and trashy objects tend to be lower on that scale, you can increase your discrimination setting on a detector to ignore everything below a given threshold.

Discrimination tends to go hand-in-hand with notching, which isolates and filters out specific parts of the scale instead of disregarding everything below the discrimination line. You might, for example, notch out pull-tabs while leaving everything that can be found both above and below those pull-tabs on the scale.

Frequency

A detector's operating frequency reflects the number of times per second that its coil pulses out a search field. It's measured in kilohertz (kHz), with 1kHz equal to 1,000 transmissions of the magnetic field per second. It's not something you really need to worry about, other than knowing that, in general, lower-frequency detectors are better at discriminating between trash and treasure, while higher-frequency metal detectors are better at gold prospecting.

Ground Balance

Different kinds of soil are packed with different levels of natural mineralization, and mineralization can throw off a detector, causing it to beep and stutter erratically. To combat this, some detectors feature either automatic or manual ground balancing, which takes into account the level of mineralization in the soil you're scanning and filters it out. Detectors with automatic ground balancing do this constantly, though often not particularly well. Manual ground balancing requires you to change certain settings every so often, but it gives you a lot more control over your device. Detectors with fixed ground balancing are factory-preset to certain levels of mineralization; if you want to deal with difficult soil, you'll need to rely on the sensitivity knob.

Prospecting

When a hobbyist uses a metal detector to search specifically for gold nuggets (actual, raw gold that hasn't been worked by human hands) they're prospecting. This can be done with any detector, but dedicated gold detectors with higher operating frequencies are preferred. They're also far more finicky and expensive than general-purpose detectors, with a much lower success rate thanks to their propensity for locating trash objects. 

If you're a beginner, you'll probably want to stay away from gold detectors. You'll still be able to find gold and jewelry with general-purpose detectors, and you'll have a lot more fun finding relics and coins in the process.

Search Coil

The search coil is the big circular apparatus on the bottom of a metal detector that you sweep back and forth over the ground. Coils are nearly always waterproof, allowing you to search in shallow water for metal that might be buried in the mud around the banks of a lake or in the wet sand on a beach. They also come in a wide variety of sizes and shapes. Generally speaking, the bigger the search coil you use, the deeper your detector can search for metal, but the harder it'll be to pick out good finds in a trashy area. This is because a bigger search coil emits a larger search field, and a detector can only see one object in its field at a time. 

If there's not a lot of metal in the area and you're looking for deep treasures, a bigger coil could suit you. But if you're in a particularly trashy area where bottle caps and pull-tabs abound, a large field might see three or four pieces of metal at once, and if only one of them is valuable, you're likely to miss it. You'd want either a smaller coil, or one that emits a field of a different shape, in order to isolate the treasure and dig it up. That's where DD coils come in. 

While many coils are made up of two concentric rings, one inside the other, DD coils have two D-shaped emitters side-by-side. A concentric coil will emit a cone-shaped field into the ground, while a DD coil's field is shaped like a thick blade, long on one axis and thin on the other. With a DD coil, you can still cover the same amount of ground with every sweep of the detector, but the thinner field makes it easier to pick between objects.

Sensitivity

Sensitivity is a simple setting, or dedicated knob, on most detectors that allows you to ratchet up or down the degree to which it reacts to objects in its magnetic field. At their highest sensitivity settings, most detectors will erratically sputter from all the mineralization in the ground, regardless of their ground balance settings. For detectors with fixed ground balance, sensitivity is the only control you have over how the device reacts to mineralization. For detectors with automatic or manual ground balance, on the other hand, sensitivity settings can give you that extra edge of control when you start picking up odd signals. So if your tool starts to sputter erratically, twisting the knob should resolve this.

Target ID

The best friend of novices and veteran hobbyists alike, target ID is a feature that flashes your detector's best guess for what's under the ground on its screen. On some detectors, the ID is a simple number that reflects an object's conductivity on a scale of 1-99. With practice, you can learn that foil and gold show up under one range of numbers, zinc pennies show up under another range, and so forth. Other detectors offer graphic target ID, which essentially translates these ranges into graphical icons. This saves you the trouble of having to learn the conductivity ranges of common finds like nails and coins. 

Target ID can save you time if you're coinshooting or hunting for relics, but if you're interested in finding valuables like gold rings or lost jewelry objects that appear in the same ranges as foil, iron nails and pull-tabs on target IDs you'll need to dig up everything, regardless of what your display screen tells you. For this reason alone, many veteran detectorists prefer to ignore their target IDs, or even to use detectors without the feature, so that they aren't swayed away from digging up true treasure.

Tone ID

Tone ID is the tone that a metal detector plays, through its speakers or headphones, when it spots metal in the ground. Some detectors only have one tone, which sounds whenever you find anything, regardless of where it falls on the discrimination scale. Detectors with two tones generally have a "good" and a "bad" tone, where the good tone sounds when something is found that's most likely a coin, and the bad tone sounds when that something is most likely trash. Detectors with three or more tones play higher sounds the higher up the discrimination scale you go, creating a sort of audible target ID.