Metal Detecting Terminology

[Detector]

I'm planning on posting some Metal Detector Reviews and thought I'd better first give some of the terminology used with metal detecting so that the reviews are easier to understand.

A.T.I.
Abbreviation for Audio Target Identification. Some detectors have the ability to help identify the type of metal by giving different tones for different metals. For example gold would produce a low tone while silver produces a high tone.

Cache
Hidden treasure consisting of valuables.

Can Slaw
Generally small pieces of aluminum cans that have been hit by a lawn mower and torn into shreds.

Cherry Picking
Recovering only the good signals while ignoring questionable signals.

Clad
Also referred to as modern coinage, generally refers to coins currently being used.

Depth
As it sounds it refers to how deep a target is.

Depth Indicator
Some detectors have a display that reads a targets depth.

Discrimination(abbr. Disc.)
The ability to reject an object. The discrimination can be done on the display, tone or both. This can be helpful in determining whether you want to dig a target. you can set the discrimination to reject iron such as bottle caps and nails, aluminum pull tabs and screw caps while still accepting coins.

Display
The visual readout of information processed by the detector. A display can be very basic giving depth only, it can be mechanical with a needle or digital LCD giving target identification, depth and conductivity.

Dropped Bullet/projectile/round
A bullet/projectile/round that was dropped and never fired.

EMI(Electromagnetic Interference)
Cause by such things as power lines and even the electronic ignition of an automobile, it can cause a detector to act erratic and in some cases unusable.

Ferrous and Non-Ferrous
Generally refers to a metals iron content. Detectors can determine categorize a target as ferrous or non-ferrous to help discriminate unwanted targets. Common ferrous targets would be nails and bottle caps while non-ferrous targets include aluminum, gold, silver, copper, zinc and brass.

Frequency
A detector transmits one or more frequencies from the outside of the coil and receives them from the inside coil. As metals come into contact with the current it disrupts the signal causing the received signal to change. This change is processed by the detector and gives a response based on what it is set to accept or reject(Discriminate).

Measured in kilohertz(KHZ) the frequency greatly effects how a detector responds to metals and ground conditions. Generally the higher the frequency the more sensitive it is to low and small targets such as gold, but at a cost of depth. Lower frequencies have better ground penetration but at a cost of sensitivity to small and gold targets.

Some of the top of the line detectors deal with this by having the ability to transmit more than one frequency simultaneously giving both penetration/depth and sensitivity to small gold targets.

Ground Balance(abbr. G.B.)
Minerals in the ground can cause a detector to respond erratically so you must Ground Balance your detector so it can tell minerals from targets. Most all modern detector have auto ground balance, manual ground balance or a preset ground balance. Manual GB gives more versatility, auto GB is simpler but not always the best choice and preset is set at the factory and may not work well in some conditions.

Halo Effect
Some metals that have been in the ground over a long period of time produce a Halo Effect that increases the detectable size of a target. While there are different theories and even some people that say it's a myth, I personally have experienced the phenomenon too many times to pas it off as myth.

Hot Rocks
Highly mineralized rocks can produce a positive signal.

Keepers
Recovered items worth keeping. Rings, older coins and relics.

Negative Response
The detector gives of a tone when a target is brought near the coil. When the tone decreases or get quieter it is called a Negative Response.

No Motion/All Metal Mode
Most, if not all, detectors require motion or continuous movement of the coil for proper discrimination. No Motion or All Metal Mode is a mode that is most often used in pinpointing a target. After a target is detected switching to All Metal Mode allows you to hold your coil still and still get a response from the target.

Pinpoint/Pinpointing
determining the exact location of a target before recovery. Once a target is found in discrimination/motion mode most detectors allow the user to switch to All Metal/Non-Motion mode to aid in recovery. This allows you to move the coils very slowly over the target until the best signal is received. At this point the target is generally directly in the center of the coil.

Positive Response
The detector gives of a tone when a target is brought near the coil. When the tone increases or get louder it is called a Positive Response.

Recover
To dig up a target.

Recovery Speed
The speed at which a detector can detect a signal and then return to threshold for the next signal.

Response
An audio or visual indication of the detector that something is effecting the coils field.

Response Time
The time it takes a detector to respond to a target. A fast response time is preferred.

Sensitivity
How sensitive a detector is to external influence. Some detectors have the ability to manually adjust the sensitivity which can increase performance. To obtain the best performance a detector needs to be as sensitive as possible while still maintaining stability.

Stability
The detectors ability to maintain a steady threshold or tone is important to detecting very deep weak signals.

Sweep Speed
Refers to the action of moving the coil from side to side while hunting in a sweeping motion. Some detectors require a faster or slower sweep speed while some allow you to manually adjust how fast you can move the coil from side to side.

Target
Any object that cause the detector to respond.

Target ID
The identification of the detected object.

Threshold
The very lowest audible tone you can hear. Manually set by turning the audio tone down to where you cannot hear it and then adjusting it up until you just start to hear a tone.

Tone ID
A detectors ability to process an incoming signal and produce a tone based on it's metal type.

Tot Lot
Those playgrounds for kids often found at parks with the monkey bars, swings and other toys.

V.D.I.(Visual Discrimination Indicator)
VDI gives you a visual means to help identify a target. Generally displayed in numbers from a negative to a positive.