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Glossary of Metal detecting Terms

Posted by on August 8, 2013

All Metal: a non-discriminate control setting that  accepts detection of all metal objects, including ferrous (i.e.  iron-containing) ground minerals.

Audio ID: also known as tone ID, this metal detector feature  identifies targets via a tone that corresponds to their conductivity.

Cache: a group of objects that has been  intentionally hidden or buried.

Clad: a term for coins that are  still in circulation. With clad coins, a surface metal covers or clads a  base metal. Pennies, for example, used to be made from copper, but are  now copper-clad zinc.

Coil: also known as the head, loop,  or antenna, a coil is the metal-sensing part of a metal detector.

Coin Shooting: a slang term for coin hunting, or going  detecting specifically in search of coins.

Concentric Coil: concentric means “having a common  center.” Concentric search coils feature circular transmit and receive  windings of unequal diameters that are aligned on a common center,  producing a cone-shaped search matrix. If the wire coils/windings of a  concentric coil are on the same plane, it’s referred to as coplanar  concentric.

Conductivity: conductivity refers to how well a target allows electrical current to flow through it. For example, electrical currents freely flow around a highly conductive coin when energized by the electromagnetic field from a metal detector.

Discrimination: discrimination is a metal detector’s ability to identify buried targets based on conductive and/or ferrous properties. Based on measuring these properties, it is possible to determine valuable targets from junk targets so you can spend more time digging valuable targets.

Electromagnetic Field: an electromagnetic field is an  invisible matrix created by electrically charged objects. In metal  detectors, the electrical current moving through the transmitter coil of  the search head produces an electromagnetic field, and this field  extends to a depth perpendicular to the size of the coil. When the field  encounters metals, they generate their own fields, which can be  measured by a metal detector’s receiver coil.

Elliptical Coil: an ellipse is an extended oval shape  resembling a flattened circle. A search coil in this shape is called an  elliptical coil. Elliptical metal detector coils can be either  concentric or widescan.

Ferrous: ferrous objects (targets) contain iron and therefore are attracted to a magnet (nails, tin cans, horseshoes, etc.). Many natural and man-made objects contain iron, most of these are junk targets, although some could be valuable relics. Non-ferrous materials do not contain iron. Good targets include coins, gold rings, and copper artifacts. Examples of junk targets are bottle tops, pull tabs, and aluminum foil.

Frequency: frequency refers to how fast a metal detector sends signals into the ground. Frequency is measured in Hertz (Hz). Certain frequencies detect certain targets better than others, e.g., high frequencies find very small targets while low frequencies find deeper/larger targets.

Ground Balance: soil often contains ground  minerals,  magnetic  material composed of ferric oxide and other metals.  These  iron-bearing  materials cause loss of depth in a metal detector.  Ground  balance is  the ability to manually or electronically ignore/neutralize these  signals (sometimes called ground tracking or   ground reject).

    Ground Mineralization: naturally occurring minerals in the ground that affect a metal detector’s performance. There are two main types of ground mineralization: one is due to iron particles and can be identified by its red coloration; the other is due to salt, such as salt water beaches. Iron particle mineralization causes the ground to become magnetic and salt mineralization causes the ground to become conductive. Both forms of ground mineralization can produce false signals that mask targets. The ground mineralization illustration shows minerals in the ground producing a response to the metal detector’s electromagnetic field.

    Masking:   masking occurs when ground  minerals or buried  objects interfere with  the detection of a legitimate  find, resulting in  a mixed signal.

    Matrix:  the total detection area  covered  by a search coil’s electromagnetic field.

    Notch:   notch filtering or notch  discrimination is used  to create a range of  accepted and rejected  targets. Setting the notch  level on your metal  detector to discriminate  against certain objects means tuning out or   blocking a particular  frequency band. This is called notch reject.   Conversely, creating a  notch window of accepted frequencies is called   notch accept.

    Null:   when a metal or coin detector coil  passes over  targets that have been  discriminated against or are outside  of the  accepted notch window, a  metal detector’s threshold audio will  go quiet or drop momentarily,  i.e. go null.

    Pinpointing: refers  to the act of   determining the precise location of a target. This can  be accomplished   by manually “detuning” a metal detector, or adjusting  it to be less   sensitive, and then sweeping the target response area  again. Because the   metal detector is less sensitive after detuning, an  audio signal  should  provide a more exact location due to the strength  of the signal.

    Prospecting: treasure hunting with a metal  detector in search of gold, silver, or valuables.

    Relic Hunting: metal detecting  in quest of  objects that possess historical (and sometimes also monetary) value.

    Sweep:   the motion a metal detectorist  employs when using a  metal detector,  it usually resembles the  side-to-side  movement used when sweeping a  floor.

    Target: any metal object that can be detected by a metal detector. A target can be either valuable, such as coins, or junk like a bottle cap.

    Target ID: numbers and audio tones are produced by a metal detector to enable you to identify targets based on their conductive and/or ferrous properties.

    Threshold:   the threshold is essentially  status quo for  the listening  detectorist. The threshold is a  continuous, faint tone  that provides  an audible reference point for  ground-balancing a  detector. It also  determines the minimum sound level  for pinpointing  targets, including  deep targets in discriminate mode.

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