Metal Detecting Glossary
If you’re new to the hobby, the language detectorists use can feel like a foreign country. Everyone seems to talk about ground balance and VDI numbers and iron masking as if you already know what they mean. This page is here to fix that. Every term below is explained in plain English, the way an experienced detectorist would explain it to a friend on their first outing.
A
Air Test
Testing a detector by passing targets through the air in front of the coil, away from the ground, to see how it responds with no soil interference. An air test shows a machine’s best-case sensitivity and tone behaviour, which makes it handy for learning target IDs, but it always overstates real-world depth because it removes the effect of soil mineralisation.
All Metal Mode
A detection setting that makes the machine respond to every piece of metal it encounters, without filtering anything out. Most detectors default to a discrimination mode that rejects certain targets, but All Metal is deliberately unfiltered. It gives you maximum depth and sensitivity, which is useful in areas where you might otherwise miss deep or unusual targets. The trade-off is that you will dig a lot more rubbish.
Alloy
A metal made by mixing two or more elements, such as bronze (copper and tin) or pewter (mostly tin). Alloys matter in detecting because their conductivity, and therefore their target ID, depends on the mix rather than on a single pure metal. This is one reason a hammered silver coin and a modern cupro-nickel coin can read very differently even though both look silvery.
Audio Tones
The sounds your detector makes when it detects a target. Entry-level machines typically give you one or two tones (a low grunt for iron, a higher beep for non-ferrous). More advanced detectors offer multiple tones, or even a continuous tone scale where each target type has its own pitch. Learning to read audio is one of the most important skills in detecting. A lot of experienced detectorists dig more by ear than by screen.
B
Backfill
Simply putting the soil back into the hole you dug, and leaving the ground looking exactly as you found it. Proper backfill means the surface is flat, the turf plug is replaced and pressed down firmly, and a stranger walking past wouldn’t know anything had been disturbed. It is the single most important habit in the hobby. Landowners remember detectorists who leave a mess, and they don’t give permission again.
Beach Hunting
Detecting on the sand and shingle of beaches, which is one of the most popular branches of the hobby because beaches are constantly refreshed with lost jewellery and coins. It splits into dry sand, wet sand, and the surf line, each with different challenges. Saltwater and black sand mineralisation make beaches demanding, which is why multi-frequency and pulse induction machines are favoured there.
Bench Test
A quick test you run at home, on a table or bench, to check a detector is working correctly or to explore its settings. You pass known coins or objects under the coil and observe how the machine responds. Bench tests are useful for learning what signals different targets produce, but they are not a substitute for field testing because the soil mineralisation is completely different indoors.
BFO (Beat Frequency Oscillation)
One of the oldest types of metal detector technology, rarely found in modern machines. BFO uses two oscillating coils and detects metals by measuring the interference between their frequencies. It is simple and cheap to build but very limited in depth and target discrimination. You are unlikely to encounter a BFO detector unless you find an old one at a car boot sale.
C
Cache
A deliberately buried hoard of coins or valuables, hidden by someone in the past who intended to come back for it. Caches are the stuff of detecting dreams, ranging from a few coins in a pot to substantial hoards that meet the legal definition of Treasure. Genuine caches are rare, but the possibility is part of why field hunting is so compelling.
Clad
A detecting term, more common in the US, for modern circulating coinage of little collectable value. The word comes from coins that are "clad" with an outer layer of one metal over a different core. Clad is the bread-and-butter find at parks and beaches, useful for practice and for slowly filling the finds pouch even on a quiet day.
Coil
The round or elliptical disc at the bottom of your detector that actually does the detecting. It transmits an electromagnetic field into the ground and receives the signal that bounces back from any metal object. Coil size matters: larger coils cover more ground and can go deeper, but they are heavier and less precise. Smaller coils are better in trashy sites where targets are close together. Most detectors come with a stock coil but can be fitted with aftermarket options.
Coil Cover
A hard plastic shell that slides over the bottom of your search coil to protect it from rocks, roots, and general wear. It is worth replacing a worn coil cover rather than letting the coil itself get scratched, because a damaged coil can affect performance. They are usually cheap and specific to the coil model.
Concentric Coil
A coil design in which the transmit and receive windings are arranged as circles sharing the same centre. Concentric coils give a symmetrical, cone-shaped detection field that is excellent for pinpointing and target separation, though they can be a little noisier in highly mineralised ground than the DD design.
Conductivity
A measure of how easily electricity passes through a material. In detecting terms, conductivity determines how strongly a target responds to your detector’s electromagnetic field. Highly conductive metals like silver and copper produce a stronger, more distinct signal. Less conductive materials like gold (which has lower conductivity than you might expect) or thin aluminium foil can be tricky to hit cleanly. Understanding conductivity helps explain why your machine treats different metals differently.
Crotal Bell
A small, round, hollow cast bell with a loose pellet inside, used historically on horse harnesses and animal collars. Crotal bells are a frequent and well-loved field find, often datable by their shape and any maker’s marks, and a good example of the everyday objects that make detecting a window into ordinary past lives.
D
DD Coil
A coil design named for the two overlapping D-shaped windings inside it, arranged back to back. The DD layout produces a blade-shaped detection field that handles mineralised ground better than a concentric coil, gives good depth, and reduces ground noise. Most modern detectors ship with a DD coil as standard.
Depth Claim
The maximum depth at which the manufacturer says their detector can find a target, usually stated in centimetres or inches. These figures are typically measured in ideal conditions using a large coin-sized target and no interference. Real-world depth will almost always be less, depending on mineralisation, coil size, target size, and soil type. Treat depth claims as a rough comparison tool between models rather than a promise.
Depth Indicator
A visual gauge on your detector’s screen that estimates how deep a target is. Usually shown as a series of bars or a numerical value. It is a rough guide only. A deep reading on a small coin and a shallow reading on a large piece of iron can look identical, so never refuse to dig something just because the depth indicator says it is shallow.
Depth Rating
When applied to waterproofing rather than detection, depth rating tells you how far underwater a coil or full machine can be safely submerged. A coil rated to 1 metre submersion is fine for wading in streams or on a wet beach. Fully waterproof machines rated to 3 metres or more can be used in rivers or even light diving conditions. Always check whether the rating applies to the whole machine or just the coil.
Detectorist
A person who pursues metal detecting as a hobby. The word is used with some pride in the UK to distinguish the responsible, history-minded enthusiast (who records finds and respects the law and landowners) from the casual treasure-seeker. Recording finds with the Portable Antiquities Scheme is widely seen as part of what it means to be a good detectorist.
Digging Tool
The spade, trowel, or purpose-made digger you use to recover a target. A good digging tool cuts a clean plug that can be folded back and replaced invisibly. Serrated stainless steel diggers are popular for pasture, while a sturdy spade is needed on heavier ground. On many permissions the landowner will specify what digging is acceptable, especially on grassland.
Discrimination
The ability of a detector to reject certain types of metal and only signal for others. A machine with good discrimination can be set to ignore iron nails and ring-pull foil while still alerting you to coins. Most detectors let you adjust the discrimination level via a dial or digital setting. Set it too high and you will miss good targets; set it too low and you will dig everything. Finding the right balance for a given site is a big part of the skill.
E
EMI (Electromagnetic Interference)
Unwanted electrical noise that disrupts your detector, causing erratic chatter and false signals. Common sources include power lines, electric fences, mobile masts, solar inverters, and even another detectorist sweeping nearby. Most machines have a noise-cancel or frequency-shift function that automatically finds a quieter operating channel to reduce EMI.
Eyeball Find
An object spotted by eye on the surface rather than detected, such as a coin or piece of pottery lying on freshly ploughed soil. Sharp-eyed detectorists pick up plenty of eyeball finds, especially worked flint and pottery sherds that a metal detector cannot register at all, so it pays to watch the ground as well as listen to the machine.
Find Recording
Keeping a record of where and how deep each significant find was made, ideally with a photograph and a grid reference. Good recording turns a bag of objects into useful history and is the basis of the Portable Antiquities Scheme. Many detectorists log finds with a phone GPS so the location can be reported accurately later.
F
False Signal
A signal your detector produces that does not correspond to a real buried metal target. False signals can come from highly mineralised soil, air pockets, wet roots, electromagnetic interference from power lines or other detectors, or a sudden change in ground conditions. Experienced detectorists learn to recognise the character of a false signal, which is typically inconsistent and disappears when you approach from a different angle or slow down.
Ferrous
Containing iron. Ferrous metals are attracted to a magnet. In detecting, ferrous typically means iron-based objects like nails, bolts, wire, and scrap steel, most of which you would rather not dig. Most detectors display ferrous targets at the low end of the VDI scale and many will give a low-pitched grunt rather than a high tone. The word is from the Latin "ferrum" meaning iron.
Field Test
Using your detector in actual ground conditions as opposed to testing at home on a bench. Field testing a new machine or coil is the only reliable way to understand its true performance, because the ground mineralisation and depth conditions encountered outdoors are completely different from anything you can simulate inside.
Find
Any object you recover from the ground. In common hobby usage, "a find" usually refers to something of interest, but technically every object you dig is a find. Significant finds in the UK should be recorded with the Portable Antiquities Scheme (PAS), and certain categories of find may meet the legal definition of Treasure and must be reported to the local coroner within 14 days.
Foil
Thin scraps of aluminium, from food wrappers, cigarette packets, and bottle seals, that are among the most common trash targets. Foil is a nuisance because it reads in a low-to-mid conductivity range that overlaps with small gold, so discriminating it out risks losing gold rings and small jewellery. Many detectorists choose to dig foil signals for exactly this reason.
Frequency (kHz)
The number of times per second the search coil sends an electromagnetic signal into the ground, measured in kilohertz (kHz). Lower frequencies (3–8 kHz) penetrate deeper and handle highly mineralised ground better, making them well suited to relic and beach hunting. Higher frequencies (14–40+ kHz) are more sensitive to small targets and low-conductivity metals like gold nuggets. Multi-frequency machines transmit several frequencies simultaneously, which is why they handle varied conditions so well.
G
Gain
Another word for sensitivity on many machines, particularly those of European origin. Turning the gain up makes the detector more responsive to faint and deep targets, but also amplifies ground noise and interference. As with sensitivity, the aim is the highest stable gain the ground will allow rather than simply running it at maximum.
Grid Search
A methodical way of covering a site by walking in straight, evenly spaced parallel lines, then repeating at right angles. Gridding ensures you cover ground thoroughly rather than wandering and missing patches. Detectorists often grid a productive field in both directions because a target masked from one approach can give a clean signal from another.
Ground Balance
A setting that compensates for the mineralisation in the soil so the detector does not signal constantly to the ground itself. Almost all soil contains some iron oxide or salt content that would otherwise swamp the signal from actual targets. Ground balance strips that background noise out. It can be fixed (preset to a typical average), manually adjusted by the user, or automatic. Machines with automatic or tracking ground balance adjust continuously as you sweep, which is helpful on beaches or in highly variable ground.
Ground Noise
The unwanted chatter and interference caused by mineralised soil, salt content, hot rocks, or electromagnetic interference. Experienced detectorists learn to reduce ground noise by adjusting sensitivity and ground balance rather than simply digging every signal. High ground noise is one of the main reasons a machine that performs brilliantly in one location can seem erratic in another.
H
Halo Effect
The slight increase in detectability around a metal object that has lain in the ground a long time, caused by metal ions leaching into the surrounding soil and making the target appear larger to the detector. The halo can help you hear very old, deep targets, but it disappears the moment you disturb the object, which is why a coin that gave a strong signal can suddenly be harder to relocate once it is loose in the spoil.
Headphones
Earphones that plug into (or pair wirelessly with) your detector so you can hear faint signals clearly and pick up the subtle tone changes that mark a good deep target. Headphones cut wind and traffic noise, save battery on machines with a built-in speaker, and are considered essential kit by most serious detectorists.
Hot Rock
A rock that contains enough iron oxide, magnetite, or other conductive minerals to produce a false signal in your detector. They are particularly common in moorland, volcanic geology, and some beach environments. A good ground balance setting reduces the chance of a hot rock signalling, but in some areas you may still dig a few before you learn to recognise the tell-tale sound. Knocking two hot rocks together produces a distinctive high-pitched click rather than the duller sound of ordinary stone.
I
ID / Target ID
The alphanumeric or graphical classification your detector assigns to a detected target, usually displayed as a number or a position on a visual scale. Target ID is based on the target’s conductivity and size as the detector interprets them. A high ID number typically suggests silver or large copper; a low number suggests iron or foil. Target ID is a guide, not a guarantee. Coins can read low if they are at an angle, heavily corroded, or very small.
Iron
The most common unwanted target in metal detecting. Iron objects, including old nails, wire, cast iron fragments, and agricultural implements, litter almost every field that has been worked for centuries. Most detectors can reject iron by tone or by VDI, but iron masking means that a desirable coin lying alongside an iron nail can be hidden by the iron’s signal. Some advanced detectors have specific iron audio channels to help you hear iron alongside other targets.
Iron Bias
An adjustable setting on some modern detectors that controls how aggressively the machine treats borderline signals as iron. Raising iron bias silences more falsing from large rusty iron, but set too high it can start to mask good targets lying next to iron. It is one of the fine-tuning controls that separates a clean, quiet hunt from one full of digging scrap.
J
Junk
The catch-all term for the unwanted modern metal you dig: ring-pulls, bottle caps, foil, shotgun cartridge ends, scrap iron, and the like. Sorting and binning your junk responsibly (rather than leaving it on site) is part of good detecting etiquette, and a "junk pouch" separate from your finds pouch keeps the rubbish away from the keepers.
K
kHz
Short for kilohertz, the unit used to describe a detector’s operating frequency. See Frequency (kHz) above for what the number actually means and how higher and lower frequencies suit different targets and ground.
L
Lead
A soft, dense metal that turns up constantly on old sites, from musket balls and fishing weights to offcuts, window came, and shapeless lumps. Lead reads in a broad mid-conductivity range and is worth digging because the same signal range holds many good targets, and lead itself can be historically interesting (musket balls and weights especially).
Loop
Another name for the search coil, used more often in older literature and by some manufacturers. If a guide mentions changing the "loop", it means fitting a different coil.
M
Masking
When a strong or disruptive target prevents the detector from registering a nearby smaller or weaker target. Iron masking is the most common type: a large iron object creates a signal that drowns out the coin lying half an inch away. Masking is one of the main reasons productive fields can still yield finds after years of detecting. Changing coil size, direction of approach, or detection frequency can sometimes uncover targets that were previously masked.
Mineralisation
See Soil Mineralisation. The general term for the conductive iron and salt content of the ground that interferes with detection and has to be managed with ground balance and sensitivity.
Motion Mode
A detection mode that requires the search coil to be moving to produce a signal. Most modern detectors operate in motion mode because it allows better discrimination and more stable ground balancing. A stationary coil in motion mode will not signal, which can be a nuisance when you are trying to pinpoint a target. This is why you switch to pinpoint mode once you have located a signal.
Mudlarking
Searching the foreshore of a tidal river, most famously the Thames in London, for objects revealed by the tide. Mudlarking overlaps with detecting but is often done by eye. In the UK it requires a permit from the relevant authority (for the Thames, the Port of London Authority), and finds should be recorded with the Portable Antiquities Scheme.
Multi-Frequency
A detection technology that transmits multiple frequencies simultaneously rather than one fixed frequency. This lets the detector handle a wider range of target types and soil conditions in a single sweep. Major multi-frequency systems include Minelab’s Multi-IQ and Simultaneous Multi-Frequency (SMF), and XP’s Full Band Spectrum (FBS). Multi-frequency machines are more expensive but are genuinely more versatile, particularly on saltwater beaches where single-frequency machines often struggle.
N
NCMD (National Council for Metal Detecting)
The main representative body for metal detecting in the UK. The NCMD lobbies on behalf of the hobby, provides member insurance (important for landowner permissions), and promotes responsible detecting and the recording of finds. Many detectorists join either the NCMD or the alternative Federation of Independent Detectorists (FID) largely for the public liability cover.
Non-Ferrous
Containing no iron, and therefore not attracted to a magnet. Non-ferrous metals include the ones detectorists most want: gold, silver, copper, bronze, lead, and aluminium. Most detectors display non-ferrous targets in the mid-to-upper part of the VDI scale and give a higher-pitched tone than iron.
Notch Discrimination
A more precise form of discrimination that lets you accept or reject specific narrow ranges of the target ID scale, rather than simply accepting everything above a set threshold. For example, you can notch out pull-tabs (which typically read in the mid-range alongside some gold rings) while keeping coins. The challenge is that target ID values overlap between desirable and undesirable objects, so notching always involves compromise.
Null
The brief period of silence some detectors produce when the coil passes over a strongly rejected target. Rather than giving no response at all, the machine actually dips briefly into silence to tell you that something is there but it has been discriminated out. A null can be a useful clue that a very large iron object or a heavily conductive target is present.
Nugget
A naturally occurring lump of native metal, almost always meaning gold in a detecting context. Nugget hunting (or gold prospecting) is a specialist branch using high-frequency VLF or pulse induction machines, common in goldfields such as Australia and the western US. Gold’s low conductivity makes nuggets a challenging target that demands sensitive, well-balanced equipment.
O
Overshoot
A brief false high-tone or jump in the target ID that some detectors produce at the edges of a large iron object, where the signal "overshoots" into the non-ferrous range. Learning to recognise overshoot, which is usually inconsistent and only sounds off from certain directions, saves you from digging large bits of iron that briefly pretended to be silver.
Open Permission
An agreement from a landowner that lets you detect their land freely, as opposed to a one-off or time-limited arrangement. A good open permission, ideally in writing, is one of the most valuable things a detectorist can have, because it lets you return repeatedly and learn a site over many seasons.
P
Patina
The natural surface layer that forms on metal over time, such as the green on copper and bronze or the toning on old silver. A genuine, undamaged patina is prized by collectors and finds recorders because it shows the object is undisturbed and helps with dating. Harsh cleaning that strips patina can destroy both the historical value and the appearance of a find.
PAS (Portable Antiquities Scheme)
A voluntary scheme in England and Wales for recording archaeological objects found by the public, run through a network of Finds Liaison Officers. Recording your finds with the PAS adds to the national archaeological record and is considered a core responsibility of ethical detecting, even for objects that are not legally Treasure.
Permission
The landowner’s consent to detect on a particular piece of land. You must have permission for any land you detect, as all land in the UK belongs to someone, and detecting without it is trespass (and on scheduled monuments, a criminal offence). Securing permissions, usually by politely approaching farmers and landowners, is a fundamental skill of the hobby.
PI (Pulse Induction)
A detector technology that uses a different operating principle from VLF. PI machines pulse a strong magnetic field into the ground and measure the decay of the return signal. They handle mineralised soil and saltwater very well, and can achieve exceptional depth on large targets. Their main weakness is poor target discrimination, which means you tend to dig everything. PI machines are the tool of choice for serious beach and surf detecting and for deep relic hunting, but they are not ideal for general detecting in trashy sites.
Pinpoint Mode
A secondary operating mode you switch into once you have found a target, to determine its exact location before you dig. In pinpoint mode the detector does not discriminate and it does not require coil movement, so you can hold the coil still and sweep slowly in a cross pattern to find the precise centre of the signal. Getting good at pinpointing saves a lot of unnecessary widening of holes.
Pinpointer
A handheld probe-style device, separate from your main detector, that you use inside the hole once you have started digging. It points to the location of the target within the spoil or the hole wall with an audio signal or vibration. A good pinpointer makes recovery faster and greatly reduces the chance of damaging finds with the spade. The Minelab Pro-Find and Garrett Pro-Pointer AT are the most widely used examples.
Plug
The neat section of turf you cut and lift to reach a target, ideally hinged on one side like a flap so it can be folded back and replaced exactly. A clean plug that beds back down invisibly is the hallmark of a careful detectorist and the key to keeping landowner permissions.
Probe
Another name for a pinpointer. The term is also used informally to describe the act of pressing your hand or tool into the spoil pile to feel for an object.
Pull-Tab
The detached ring or tab from a drinks can, one of the most common and frustrating trash targets because it reads in the same conductivity range as many gold rings. The "pull-tab problem" is the classic dilemma of detecting: discriminate them out and you risk losing gold, or dig them all and accept a lot of aluminium.
R
Reactivity
XP’s term, and a concept shared across brands, for how quickly the detector recovers between targets and responds to closely spaced finds. High reactivity helps separate good targets from nearby iron in trashy ground, at some cost to raw depth. It is essentially the same idea as recovery speed.
Recovery Speed
How quickly a detector’s electronics reset after registering one target, ready to detect the next one. A fast recovery speed matters in trashy sites where good targets are separated from iron by only a few centimetres. A slow recovery speed can mean that a coin lying inches from a nail is hidden because the machine is still processing the nail’s signal when the coil passes over the coin. Most mid-range and high-end machines let you adjust recovery speed.
Relic
Any object of historical interest recovered by detecting. The term is used loosely and covers everything from Roman coins and medieval buckles to musket balls and Victorian household items. In the US, "relic hunting" specifically refers to searching for Civil War and other battlefield militaria. In the UK it tends to mean anything old and interesting, though certain categories of relic carry legal obligations around reporting.
Relict Landscape
A landscape that retains traces of earlier land use, often invisible on the surface but detectable in the soil. Ancient field systems, drove roads, settlement remains, and ridge-and-furrow patterns are all relict features. Detectorists who understand relict landscapes can often locate historically productive areas that have no surface indication of activity.
Ring-Pull
The older style of fully detachable can ring, and a catch-all term (along with pull-tab) for aluminium drink-can debris. Like foil and pull-tabs, ring-pulls sit in the low-to-mid conductivity range that overlaps with gold, making them the perennial trash target detectorists love to hate.
S
Salt / Saltwater
One of the most challenging environments for metal detectors. Salt is a conductor and the wet sand or water on a saltwater beach can overwhelm a standard VLF machine with false signals. Machines designed for salt beach use (either multi-frequency or PI) have specific ground balance and filtering to handle the conductivity of salt. Even these machines require careful ground balance adjustment on wet sand.
Search Coil
The same as the coil described above. The terms are interchangeable, though "search coil" tends to appear more often in formal documentation and product listings.
Sensitivity
A control that adjusts how receptive the detector is to faint signals. Higher sensitivity lets the machine detect smaller and deeper targets, but it also makes the machine more susceptible to ground noise and interference. In practice, you rarely run sensitivity at maximum. The goal is the highest stable setting for the ground you are in.
Signal
Any response your detector produces when the coil passes over a target. Signals vary by tone, strength, and consistency. A repeatable, stable signal from multiple sweep directions is a good sign that the target is real and worth digging. An inconsistent or directional signal suggests iron, a hot rock, or a very large ferrous object.
Sniper Coil
A small, tight search coil, typically between 5 and 7 inches in diameter. Sniper coils are designed for working in heavily trashy areas where targets are packed close together. The smaller detection field is more precise, allowing the machine to separate a good target from nearby iron. The trade-off is reduced depth compared to a larger coil.
Soil Mineralisation
The concentration of iron oxides, salts, or other conductive minerals in the ground. Highly mineralised soil is one of the biggest challenges in metal detecting. It creates background interference that reduces depth, triggers false signals, and makes ground balancing critical. Red or dark heavily weathered soils are often highly mineralised. Chalk, sand, and alluvial soils tend to be lower mineralisation and generally easier to detect in.
Spoil
The loose soil you remove from a hole, piled to one side while you recover the target. Checking the spoil with a pinpointer is often how you finally locate a small find, and tipping the spoil back in cleanly before replacing the plug is part of leaving no trace.
Stamped Find
A find that has a clear maker’s mark, date, hallmark, or inscription. Stamped finds are easier to research and date accurately. Stamped coins, trade tokens, buttons, and seals are all examples.
Stubble
The short, sharp stalks left in a field after a cereal crop is harvested. Freshly cut stubble, before it is ploughed back in, is a prized detecting window because the ground is accessible and recently disturbed. Landowners often grant access in the narrow gap between harvest and ploughing.
Sweep Speed
See Swing Speed. The pace at which you move the coil across the ground, which has a real effect on whether motion-mode machines register targets.
Swing Speed
How fast you move the search coil back and forth as you walk. Most detectors perform best at a steady, unhurried sweep, typically covering about one metre per swing at a consistent height of 1–3 cm above the ground. Swinging too fast can cause you to miss targets or get inconsistent readings. Many beginners rush and cover too much ground; slowing down and being methodical finds more.
T
Target
Any buried object that produces a signal. Whether it turns out to be a coin, a nail, or a bottle cap, everything your detector responds to is a target until you dig it up.
Target ID
See ID / Target ID above.
Threshold
A continuous background hum or tone that some detectors produce, which dips or rises when a target is detected. Threshold-based audio is common on older machines and on PI detectors. It gives you a constant audio reference so you can hear even very faint responses. The threshold can usually be adjusted so it is just audible without being distracting.
Token
A small disc, usually of copper or copper alloy, made to represent a monetary value. Tokens were widely used in Britain from the 17th to 19th centuries when there was a shortage of official small coinage. They were issued by merchants, taverns, and manufacturers. Trade tokens are a common and often beautifully detailed find on detecting sites of that period.
Treasure Act 1996
The UK law that defines which finds are legally "Treasure" and must be reported. In broad terms it covers gold and silver objects over 300 years old, groups of coins of the same find, and prehistoric base-metal hoards. Finders in England, Wales, and Northern Ireland must report potential Treasure to the coroner (in practice via a Finds Liaison Officer) within 14 days. Scotland operates a separate system under which all finds technically belong to the Crown.
U
Undisturbed Ground
Soil that has not been ploughed, dug, or otherwise turned over, so any objects in it lie roughly where they were lost. Undisturbed pasture can preserve finds in context and at their original depth, which is good for the archaeological record but means targets are often deeper and the landowner is usually more particular about how you dig.
V
VDI (Visual Discrimination Indicator)
A numerical scale displayed on your detector’s screen that classifies each detected target. The scale varies by machine but is commonly 0–99 or -95 to +95. Low numbers indicate highly ferrous or low-conductivity targets. High numbers indicate highly conductive metals like silver. The VDI gives you a quick reference before you decide whether to dig, but it is a probability, not a certainty. A 73 might be a large copper coin or a bottle cap depending on its size and orientation.
VLF (Very Low Frequency)
The most common type of metal detector technology in use today. VLF machines operate by transmitting a continuous sine wave into the ground at a fixed frequency and measuring the phase-shifted return signal. They offer good discrimination, adjustable frequency, and a useful balance of sensitivity and depth for most detecting scenarios. The vast majority of detectors sold for general use are VLF machines.
Volume
The loudness of your detector’s audio output, adjustable on most machines and on many headphones. Some detectors also offer separate volume control for different tone regions, letting you, for example, turn iron down so it is just audible while keeping good non-ferrous tones loud. Tuning volume carefully helps you hear faint deep signals without being deafened by strong shallow ones.
W
Wand
An informal name for a pinpointer, from its slim, pen-like shape. See Pinpointer above.
Waterproof Rating
How much water exposure a detector can handle. Ratings range from "coil only submersible" (the shaft and control box must stay dry), through IP54 or IP55 (splash and light rain resistant), to full submersion ratings for underwater use. Check carefully whether a waterproof claim applies to the whole machine or just the coil. Many mid-range machines have waterproof coils but electronics that must not get wet.
Wireless Audio
A feature on many modern detectors that sends sound to wireless headphones rather than a cable, removing a snag hazard and letting you move freely. Because standard Bluetooth adds a slight delay that would lag behind your sweep, detectors use low-latency wireless protocols so the tone arrives in time with the coil passing over the target.
Z
Zero Discrimination
Setting discrimination to its lowest possible level so the detector signals for virtually all metals. It is the same principle as All Metal Mode but applied through the discrimination control rather than a separate mode switch. Useful when searching for gold, lead, or other low-conductivity targets that might otherwise be filtered out.
More terms will be added as the site grows. If there is a term you have heard on a club dig or read in a forum that is not here, use the contact form to suggest it.