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Buyers Guide - Glossary

OVERVIEW FAQ GLOSSARY

A
 
   
Air Test:
A test performed by passing metal samples of various sizes under the detector's search coil to check target responses. This test is not an accurate indicator of ground depth penetration.
   
Alkaline:
A type of battery characterised by the ability to sustain longer periods of current drain and greater storage life than standard carbon-zinc batteries.
   
All Metal:
Describes any mode or control setting that allows total acceptance of metal targets. Usually associated with ground balance mode.
   
Audio ID:
Circuitry producing different audio tone for each target's conductivity range, eg low tone for iron, high tone for coins.
   
Auto Tune:
Circuitry which continuously retunes the detector's threshold to the initially tuned audio level at a preset rate after drift and/or target rejection.
 
B
 
   
Back Reading:
A false signal caused by a rejected target coming within one inch of, or contacting, the bottom of the search coil when operating in the discriminate mode.
   
Bench Test:
An air test to determine at what approximate discriminate settings various metal samples are rejected or accepted. The test is conducted in non-metallic area.
   
Black Sand:
One of the most extreme components of non-conductive, negative ground minerals. Also called magnetite and magnetic iron oxide.
   
Body Mount:
A method of fastening the detector's control box to expand usability for shallow water hunting. Also known as hip mount.
 
C
 
   
Carbon-Zinc:
Standard dry cell batteries.
   
Coin Depth Indicator:
A visual indicator, used in conjunction with calibrated circuitry, to show depths, in inches or centimetres, of buried coins.
   
Concentric:
A search coil configuration using one or more transmit, and one receive, winding having unequal diameters aligned on a common center, most recently arranged on the same plane and called 'coplaner concentric'.
   
Conductive Salts:
Wet salt sand which produces a positive rise, or metallic response on an air tuned threshold.
   
Conductivity:
The measure of a metal target's ability to allow eddy currents to generate on its surface.
 
D
 
   
Detection Pattern:
The densest or strongest region of the search coils electromagnetic field where detection occurs. It is balloon shaped and changes in size directly in proportion to target surface area.
   
Detuning:
Adjusting the audio threshold into the null or less sensitive tuning zone. It is also a method of narrowing a target's signal width manually for precise pinpointing. This is accomplished by returning to audio threshold over the target response area.
   
Discrimination:
Adjustable circuitry which ignores or nulls audio responses from a specific conductivity range allowing positive responses to be heard from metals higher in conductivity above the discriminate control setting. Designed primarily to eliminate audio response from unwanted metals.
   
Drift:
A loss of threshold tuning stability caused by temperature change, battery condition, mineral content, and/or detector design.
 
E
 
   
Eddy Currents:
Small circulating currents produced on the surface of metal by the transmitted electromagnetic field. These currents then produce a secondary electromagnetic field which is then detected by the search coil receiver windings, resulting in inductive imbalance between the windings.
   
Electromagnetic Field:
An invisible force extending from top to bottom of the search coil and created by the flow of alternating oscillator frequency current around the transmit winding.
 
F
 
   
Faraday Shield:
A metal foil wrapping of the search coil windings for the purpose of eliminating electrostatic interference caused by wet vegetation.
   
Ferrous:
Descriptive of any iron bearing material.
   
Ferrous Oxide:
An oxidised particle of iron which becomes non-conductive and makes up the natural negative ground mineral matrix. Hematite, which is also an iron oxide, will respond as positive or metallic.
   
Frequency:
The number of complete alternating current cycles per second produced by the transmit oscillator. Measured in Hertz (Hz). VLF = Very Low Frequency; LF = Low Frequency; MF = Medium Frequency; HF = High Frequency.
 
G
 
   
Ground Balance:
A state of operation in which specialised circuitry can be adjusted to ignore the masking effect that iron ground minerals have over metal targets.
   
Ground Balance
(Operator Adjust):
A feature requiring a manual control adjustment procedure to neutralise the effects of negative minerals in the search matrix.
   
Ground Balance
(Factory Preset):
A feature which eliminates the manual ground balance control and its adjustment from the operators set up procedure. This adjustment is performed internally by the factory to optimise operation over an average range of non-conductive soils.
   
Ground Filter:
Complex circuitry found in motion type detectors which separates mineral signals from metal signals, allowing the metal signal to be further processed by the discrimination circuitry.
 
H
 
   
Hot Rock:
A rock which contains a higher concentration of non-conductive ground minerals than the surrounding matrix to which the detector is balanced. A metallic (positive) response will be heard in the motion and non motion modes, and a null or negative drop in threshold is heard in the all metal ground balance mode over these rocks.
 
I
 
 
J
 
 
K
 
 
L
 
   
LCD (Liquid Crystal Display):
Used on a metal detector as a graphic visual indicator.
   
LED (Light Emitting Diode):
A semiconductor which produces an illuminated visual response.
 
M
 
   
Matrix:
Refers to the total volume of ground penetrated by the transmitted electromagnetic field which may contain varying amounts and combinations of minerals, metals, salts and moisture.
   
Metal:
Metallic substances: iron, foil, nickel, aluminium, gold, brass, bronze, lead, copper, silver, etc.
   
Metal Detectorist:
A person operating a metal detector in the field. This name is preferred by many to 'treasure hunter'.
   
Mineral Free Discriminator:
Detector that can reject or ignore trash metals while simultaneously eliminating or balancing ground mineralisation.
   
Mineralised Ground:
Any soil that contains conductive or non conductive components.
 
N
 
   
Negative Ground:
Soil that contains non-conductive minerals which have a negative or nulling effect on air-tuned threshold.
   
Neutral Ground:
Soil lacking non-conductive or conductive mineral properties. It lacks mineralisation.
   
NiCad (Nickel Cadmium):
A rechargeable battery.
   
Non-ferrous:
Not of iron; metals including gold, silver, copper, lead, tin, brass, bronze, etc.
   
Non-Motion:
Mode of operation that does not require search coil movement to trigger target response.
   
Notch Accept:
Operation whereby all target responses are 'tuned out' except those the instrument is adjusted to accept in the notch window.
   
Notch Discrimination:
Circuitry which allows a desirable window of targets to be accepted within the rejection range of unaccepted targets.
   
Notch Level:
A control used to select the target level of conductivity which the notch filter will act upon.
   
Notch Reject:
Operation whereby all targets within the notch width (at the chosen notch level) will be 'tuned out'.
   
Null:
Zone just below audible threshold in detector tuning. The term also refers to the momentary drop, or quiet response, of threshold audio as the search coil passes over a discriminated or rejected target.
 
O
 
   
Overlap:
The amount of search coil swing advance not greater than the search coil's physical diameter.
 
P
 
   
Pinpointing:
Finding the exact target location with respect to a search coil's designated centre. Accomplished by interpreting the centres of audio response width in perpendicular directions or scans.
   
PI (Pulse Induction):
A metal detector with a transmitter circuit that pulses an electric current into the ground before quickly shutting down. The eddy currents dissipate immediately from wet salt sand and other ground minerals because they are poor conductors. Because they are better conductors, metals hold the eddy currents, and when the receiver circuit comes on, it picks up the returning signals from metal objects.
 
Q
 
 
R
 
   
RF-Two Box:
Radio frequency detector with 2 separate coils, the detector is capable of detecting large, deep objects while naturally ignoring small targets such as nails and individual coins.
 
S
 
   
Scan:
The effective search coil detection width. Also refers to search coil movement over the ground.
   
Scrubbing:
Search technique in which the search coil is pressed and held in contact with the ground in order to maintain an even audio threshold. With newer detectors, this technique is used to gain depth.
   
Search Coil:
A circular (or other shaped) plastic housing containing single or multiple transmit and receive wingdings in a specific orientation or configuration to emit and receive signals from ground and targets. (Also called a 'loop' or a 'coil'.)
   
Search Coil Cable:
An electrostatically shielded cable of conductors (wires) which convey signals to/from the search coil and control housing.
   
Sensitivity:
The measure of capacity of a detector to perceive changes in conductivity within the detection pattern. Generally, the more sensitivity a detector can smoothly provide, the more depth it will achieve.
   
Silent Search:
(= silent operation) A detector capable of producing a target signal while operating below the threshold audio.
   
Skid Plate:
(=coil cover or scuff cover) A protective cover for the search coil bottom.
   
Slow Motion:
A description of search coil speed required to operate the motion discriminate mode.
   
Sweep:
The motion employed in moving the search coil across the ground.
 
T
 
   
Target Masking:
Occurs when large pieces, or high concentrations, of trash metals drive the threshold into the null zone, suppressing weaker responses from deeper or smaller targets.
   
Ten-Turn:
A control which can be manually rotated ten times to cover the full electrical range of the function. Usually associated with tuning or ground balance function.
   
TH'er:
Treasure Hunter
   
TH'ing:
Treasure Hunting
   
Threshold:
An audible reference point for tuning the detector in order to ground balance it. The threshold tone also establishes the minimum sound level for deep targets in the discriminate mode.
   
TR (Transmit/Receive):
The term used to describe an early type of detector, still produced by some manufacturers. Electromagnetic field distortion caused by mineralised ground interferes with depth penetration because this type of detector does not ground compensate. It does however balance salt water effects. Therefore, it is primarily used for searching in salt water and on low mineral salt water beaches.
 
U
 
 
V
 
   
Visual ID:
Visual indication used to identify targets.
   
VLF/DISC:
Term associated with detectors capable of mineral free operation in both the discriminate and all metal mode.
   
 
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