If a detectorist doesn't understand how their detector fully works, potentially they could be missing gold nuggets.  Metal detectors work on the principle of conductivity.  All metal objects, whether ferrous or non-ferrous are conductive. That is, heat and electricity can flow through them.

A metal detector creates an Electro-Magnetic Field which penetrates into the ground.  When this field comes across a conductive metal object, the search coil senses a charge in the field, and thus, detects the objects buried below.  A signal is then sent to the control box, which drives a loudspeaker, meter or headphones and emits a noise, alerting the operator of a potential object. 

Metal detectors react to the surfaced area of an object, not its mass.  The larger the surface area, the deeper you will be able to detect an object.  For example, a coin lying flat will be detected at a greater depth than the same coin standing on it's edge.  In addition to metals, a detector may react  to iron ores, magnetic non-conductive minerals and beach salts.  These non-metallic substances are known as mineralized ground and cause a detector to produce a false signal or ground noise.

To eliminate this ground noise, the detector has a ground balance function to compensate for the levels substances in the ground being searched.

"Detector Technology"

What is Automatic Ground Tracking (AGT)?

AGT refers to the ability of the detector to track the changes in ground mineralization and automatically adjust the ground balance to suit.  This ensures perfect ground balance and full detection depth and eliminates the need for the operator to stop and manually adjust the detector as the ground conditions change.  The Minelab SD2100 does not have auto ground  tracking. 

What is Very Low Frequency (VLF) Technology?

Conventional VLF detectors transmit a continuous magnetic field into the ground on one set frequency.  This VLF technology as the name implies, operates at low frequencies.  The conventional range is from 3 kHz to 50 kHz.

Minelab now produces detectors which operate at slightly higher than 50 kHz and lower than 3 kHz frequencies to gain greater depth and sensitivity.  Some models operate in a number of frequencies which allows you to choose the most effective range for the particular type of detecting.  The Minelab GT15000, 16000, American Gold Striker, XT17000, XT18000 & latest Eureka Gold all use this VLF technology. 

What is Broad Band Spectrum (BBS) Technology?

Unlike other metal detectors which operate on one or two frequencies, BBS technology transmits multiple separate frequencies over a range of 1.5 kHz to 25.5 kHz.  All multiple frequencies are transmitted at the same time, spread over a wide spectrum.  BBS technology means you have more depth, greater and more accurate discrimination.  The Minelab Sovereign series & Excalibur use this technology. 

What is Full Band Spectrum (FBS)?

FBS technology is a further development of Minelab's BBS Multi Frequency Technology.  This Technology is unique to Minelab, providing greater depth and improved target identification in most soil conditions.  FBS refers to the use of 28 frequencies operating simultaneously over a range from 1.5kHz to 100kHz.  FBS Technology means that a wider range of targets can be located at greater depths.  The Minelab Explorer II & the latest Minelab Quattro use this technology. 

What is Multi-Period Sensing (MPS) Technology?

It transmits a stream of alternating short and long pulses of magnetic field into the ground.  These pulses cause metal objects in the ground to produce a changed magnetic field of their own.  MPS technology is able to locate metal targets up to four times the depth of conventional detectors.  MPS also means that very small targets may be found in the most difficult ground and you will dig less ground signals.  The Minelab SD2100, SD2100v2, SD2200d, SD2200v2 & the GP Extreme detectors all use this type of technology. 

What is Dual Voltage Technology (DVT)?

DVT refers to changes in the voltage used to create the electro-magnetic field transmitted from the coil into the ground.  By using two different voltages (DVT) the possibilities of magnetic saturation of the ground is lessened.  Thus, detectors using DVT have an increased ability to balance out ground mineralization providing increased depth and greater sensitivity compared with other detectors.  The latest Minelab GP3000 Metal Detector uses this technology.  What to see more on the Minelab GP3000?  "Click Here!"

What are Operating Frequencies?

Frequencies in a metal detector are referred to in kHz (kilo hertz) which is the number of times a signal is transmitted into the ground as received back per second.  The lower the detector's frequency, the deeper it will penetrate.  However, its sensitivity to smaller targets may be reduced.  On the other hand, the higher the detector's frequency, the higher its sensitivity to even the smallest targets, but it may not penetrate as deeply.

Generally, gold detectors operate at a higher frequency for locating small gold nuggets.  Coin, relic and treasure hunting detectors operate at lower frequencies for greater depth penetration.

Courtesy of Minelab World Adventurer 1999 edition & Product Catalog.

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