How to metal detect: Part 6 – Metal Detecting Terms

Metal Detecting Terms GlossaryThe following glossary of terms will help you understand metal detecting terminology.

Air Test or bench test– An air test is a test of targets outside the ground. When using a metal detector for the first time it’s a good idea to run various targets across the coil to see what kind of signals they produce and general depth capabilities.

All Metal Mode– All metal mode refers to the setting on a detector so that it will pick up all metal objects. In other words any metal object will produce a signal and no targets are rejected or discriminated out. (see discrimination).

Audio signal or tone– When a detector is run across a metal object it will produce a sound known as an audio tone or signal.

Conductivity– When a metal object is passed through a magnetic field small electromagnetic fields known as eddies will be generated. Conductivity is a measurement of the ability of the metal to generate these fields. Highly conductive metal such as silver will product stronger magnetic fields than lower conductive targets such as lead.

Control box– The part of a metal detector that houses the electronic circuitry. Buttons, lcd screens, and the battery compartment are typically located on the control box.

Depth– How deep the metal detector can detect a target. The larger the metal object the deeper it can be detected. The typical range of depth for a general machine is about 12″ on coin sized targets.

Discrimination– Most metal detectors have a feature called discrimination in which unwanted targets can be eliminated. Each metal object has a different conductivity level so by setting the discrimination to reject lower targets they will not produce an audio signal. (See also Notch Descrimination).

Double D coil– The DD search coil had become very popular as a great general coil. There are two “D” shaped winding which creates a narrow and long search field which is great for sniffing out good targets amongst trash items. DD coils also offer excellent depth capabilities.

False signal or falsing– When a detector produces an audio signal when no significant object is present. For example if there is a lot of mineralization in the soil the detector might produce a coin signal even though there is no coin there.

Ferrous– Metal containing iron that will stick to a magnet is considered ferrous. Metals such as silver, gold, and copper are considered non-ferrous.

Frequency– The number of electrical cycles per minute, usually measured in KHZ or kilohertz. High frequency units do better on low conductivity targets such as gold and smaller objects. Low frequency metal detectors do better on high conductivity targets such as silver but don’t do as well on small items.

Ground balance– Different soil conditions have different amounts of mineralization and conductivity. Ground balancing a machine ensures that the machine is ignoring the ground but not other objects. An improperly ground balanced machine can give false signals or have reduced depth capabilities. Manual ground balance means that the user can adjust ground balance manually and auto means that the machine will auto ground balance itself.

Mineralized soil– Ground containing minimization that effects the metal detectors ability to operate.

Notch Discrimination– Some detectors have a feature called notch discrimination. For example if a detector has 10 notches, each notch would represent a range of targets based on their conductivity. Using notch discrimination it’s possible to eliminate certain targets such as pull tabs while still receiving an audio signals on lower conductive targets such as nickels and higher conductive targets such as coins.

Pinpointer– A handheld device used to find the target once you dig the hole. Pinpointers act as a miniature metal detector so you can hone in on your target and find it quickly.

Pinpointing– Pinpointing refers to locating a target under the metal detectors search coil. When an audio signal is received the target is usually directly under the coil. By turning 90 degrees you can create a virtual “X” on the ground that shows precisely where the target is.

Pulse Induction– Pulse induction detectors only have one winding in the coil which both sends and receives the signal. They typically go much deeper than VLF machines but also lack the ability to discriminate targets well. PI metal detectors are great for hunting non trashy areas such as beaches or ocean floors but do very poor in trashy areas such as parks or residential yards.

Recovery time– The time it takes for the electronic circuitry of your metal detector to recover after passing over a target. If a coin is very close to trash it’s very important that the metal detector have the ability to recover quickly after the trash signal so that it picks up the coin signal. Detectors with fast recovery have a significant advantage in trashy areas.

Search coil– The part of the metal detector that you sweep over the ground. It houses the electrical windings that send and receive signals.

Sensitivity– The setting that adjusts how sensitive the unit is to detecting targets. A metal detector set on high sensitivity will detect deeper targets but may also experience more false signals. Setting the sensitivity to a lower number will reduce the depth capabilities but also have much less falsing.

Stability– The ability of the metal detector to ignore interference from outside electrical sources such as power lines.

Target separation– The ability of a metal detector to identify targets that are located in close proximity to each other. For example if a unit has excellent target separation, it means that it does very good in trashy areas where good targets are very close to trash targets.

Threshold– An audio hum heard on some machines that allows for optimal performance and audio sensitivity. The threshold hum will be interrupted by even the deepest faint signals so the user can hear them. When the search coil passes over a discriminated target the threshold will go silent which lets the user know there is trash below.

Tone ID– An audio signal which identifies the target based on its composition. A single tone metal detector will give the same audio signal no matter what target is detected. A multi tone unit will produce a higher pitched tone on targets such as coins and a lower pitched tone on lower conductivity targets such as lead.

VLF (Very low frequency)– VLF metal detectors have two separate loops inside the search coils. One sends a signal and the other receives a signal. When the sent signal hits a metal object, the object will generate a magnetic field which is then picked up by the receiver and sent to the control box to be analyzed. Most general detectors on the market today are VLF.