Glossary of Detecting Terms
AC (Alternating Current) - Metal detector modes that require loop motion to
respond to metal.
Air Test - Testing a metal detector's response to various metallic samples
with the loop held away from the ground.
All-Metal - Describes any mode or control setting allowing total acceptance
of all types of metal targets, iron and non-iron.
Audio Identification - Circuitry or mode producing different audio tones
(pitches) for different target types.
AutoTrac (Automatic Ground Tracking) - A feature that continually and
automatically readjusts the ground balance (ground rejection) of a metal
detector during searching.
Back Reading - A false target response caused by either overloading due to a
very strong target near the loop, or a rejected trash target very close to
the loop.
Black Sand - One of the most extreme components of nonconducting negative
ground mineralization. Also called (Fe304), magnetite, iron oxide, magnetic
sand.
Cache - Intentionally buried or secreted hoard of valuables.
Conductive Salts - One of the major mineral types which makes up the
positive ground matrix. Wet ocean salt/sand will produce a positive
indication much like a metal target.
Conductivity - The measure of eddy currents of electricity that generate on
a metals surface.
Custom Program - Feature choices on a computerized metal detector that are
then saved or stored for future use.
DC (Direct Current) - Used to refer to metal detector modes that do not
require loop motion to respond to metal targets.
Detection Pattern - The shape of the electromagnetic detection field
generated by a metal detector's loop.
De-tuning - A method of narrowing a target signal's width and length for
precise pinpointing.
Depth - How deep a detector can respond to metal targets.
Depth Reading - Feature that indicates how deep a target is in the ground
before digging.
Discrimination - Adjustable feature that can ignore or respond to different
metal types based on their amplitude and phase. Used to cancel responses of
unwanted trash metals.
Drift - A loss or increase in threshold caused by the passage of time or
variations in temperature..
Eddy Currents - Small circulating currents of electricity on the surface of
metals produced by external electromagnetic fields.
Electromagnetic Field - An invisible force extending from the loop created
by the flow of alternating oscillator frequency current around the transmit
winding.
Elliptical Coil - A loop with an ellipse (oval) shape.
False Signal - Erroneous signal caused by non-metal items.
Faraday Shield - Conductive coating inside loops, loop cables, and control
housings to eliminate electrostatic interference.
Ferrous Oxide - Decomposed particles of iron (mineralization).
Frequency - The number of complete alternating current cycles produced by
the transmit oscillator per second. Measured in Hertz (Hz) or cycles per
second.
Frequency Shift - Changes the operating frequency suppressing the
interference (cross talk) between detectors.
Fringe Target - A target so deep or so small as to be barely detectable with
a metal detector.
Ground Balance - A feature that can be adjusted to ignore the masking effect
ground minerals have over metal targets.
Ground Matrix - Total volume of undisturbed ground, usually contains varying
amounts and combinations of minerals, moisture, and salt. In an undisturbed
condition the ground matrix can exhibit numerous phenomenons regarding metal
detector performance.
Hipmount - A configuration where the control box of a metal detector is
mounted on the operators hip limiting the weight one has to sweep to that of
the loop and rod assembly.
Hot Rock - A rock that contains a higher concentration of minerals than the
surrounding ground.
Interference - Hindrance of performance due to sources outside a metal
detector causing static and unwanted or false signals.
LCD (Liquid Crystal Display) - A digital display used for graphic visual
indications as an alternative to the use of meters.
Memory - A computerized metal detector's ability to retain operator selected
settings for future use.
Menu - A display screen that allows the operator to choose among different
features.
Metal - Metallic substances: iron, foil, nickel, aluminum, gold, brass,
lead, copper, silver, etc.
Meter - An analog component which provides visual indications regarding a
metal target (Alternative to LCD displays).
Mineralized Ground - Any soil or sand that contains conductive and/or
magnetic components (minerals).
Mixed Mode - A special metal detector mode that combines all metal and
discriminate features into one operating mode.
Mode - A condition or feature of operation selected by the operator for
specific functions.
Motion Instrument - A detector type that requires search loop movement to
activate the signal from a metal target.
Microprocessor - An electronic component (chip) that can be programmed to
perform a variety of functions and control a variety of features.
Negative Ground - Soil containing mostly magnetic minerals.
Neutral Ground - Soil that contains no significant minerals.
Nicad (Nical Cadmium) - A battery type that can be recharged.
Non-Ferrous - Not of iron . Metals of the precious and semi precious class
(i.e. aluminum, brass, lead, gold, silver, copper).
Non-Motion - Mode that will respond to metals with or without movement of
the loop.
Notch Discrimination - Discrimination circuitry that allows an area of the
discrimination range to be accepted or rejected independently of the
remaining discrimination range (a window of acceptance or rejection within
the discriminate range).
Notch Width - Finite range of a notch discrimination setting (how wide of
window is accepted or rejected).
Null - A decrease in sound caused by rejection of targets or ground
mineralization.
Oscillator - An electronic component or circuitry designed to generate a
specific rate of current frequency to power the loop's transmit winding.
Overlap - Advancing each sweep of the loop in small increments to insure
good area coverage. Each sweep should overlap the last by at least 50%.
Overload - Occurs when the receiver of a metal detector becomes overwhelmed
due to too much signal (ground and/or target).
Overshoot - A false signal heard as the loop passes over a rejected target
when using a non-motion discriminate mode in combination with automatic
tuning. Excessive tuning restoration pushes the audio above the threshold
level creating a positive response at the edges of target detection.
Phase - The length of time between eddy current generation sustained on a
metals surface and the resultant secondary electromagnetic field effect on
the loops receive winding. Relates to target conductivity.
Pinpointing - Finding the exact target location with respect to the loops
physical center.
PI (Pulse Induction) - A type of metal detector circuitry that operates
differently than the standard Transmit Receive or Very Low Frequency
instruments. Primarily recommended for better results in salt water.
Positive Ground - Soils that contain conductive components such as salt.
Preset - A control setting or marking determined to work well for average
conditions.
Preset Program - A selection of a computerized metal detector that
automatically selects all the features suited to a particular type of
searching condition.
Prospecting - Searching for gold in its natural state (nuggets).
Rejection - Non-acceptance or cancellation of a target response by
discrimination circuitry.
Relic - An artifact of the past.
S.A.T. (Self Adjusting Threshold) - Automatically resets the threshold to
correct for any minor ground, temperature, or electrical changes that
typically cause threshold variations.
Scrubbing - Sweeping the loop with contact to the ground.
Searchcoil - (See Loop)
Sensitivity - Measure of a detector's ability to respond to targets within
the detection pattern. Usually indicates the capability to respond to small
targets rather than maximum detection depth.
Signagraph - A graphic display of a pattern characterizing a targets
electrical and/or magnetic properties.
Signal - An audio response or visual indication alerting the operator that a
metal target has been detected.
Silent Search - Capability of a metal detector to respond to metals without
a threshold or background sound being heard continually during searching.
Stability - The ability of a metal detector to maintain smooth operation
without interference or unstable operation.
Target - Any object that causes a metal detector to respond.
Target Masking - When large size or high concentrations of trash metals, or
extreme ground mineralization, drive the threshold into the null zone
suppressing weaker positive responses.
Ten-Turn Control - A control knob which can be rotated ten times to cover
the full electrical range of the feature.
Test Garden - A mapped plot of buried targets at various depths to aid in
learning the characteristics of a metal detector.
TH'er, TH'ing - Universal word contractions for treasure hunter and treasure
hunting.
Threshold - The background hum heard continually during the use of a metal
detector indicating the most sensitive audio.
Tone Control - An adjustment for audio frequency or pitch.
Touch-Pad - Switches encapsulated in plastic or that allows the operator to
select different functions or features.
Transmit Coil - A coil of wire inside the loop that creates the primary
electromagnetic field.
TR (Transmit Receive) - Term used to describe early metal detector
technology. Usually describes non-ground rejecting detectors or modes.
Two Box - A metal detector that has the transmit and receive coils mounted
in separate housings. By enlarging and separating the transmit and receive
coils great depths regarding large metal items can be achieved. Also called
cache detectors.
Viewing Angle - A liquid crystals display adjustment for contrast allowing
optimum visibility for various light conditions.
Visual Discrimination - The ability of a metal detector to determine trash
or non-trash by means of visual indications.
Visual Discrimination Indication (VDI) - A visual indication as to the type
of target a metal detector is detecting.
VLF (Very Low Frequency) - Generally used to refer to metal detectors that
can cancel the effects of ground mineralization, typically with operating
frequencies in the 3-30 kHz range.
VLF/DISC - A detector that can cancel ground mineralization while at the
same time discriminate against trash.
Voltage Regulator - Circuitry that controls the amount of electricity
supplied to operate a metal detector with no loss in performance over a
specific voltage/current range.
Zero Discrimination - Used to describe detectors whose discrimination
control allows the acceptance of all types of metals when set to the zero
position.