Metal Detector Technology

Continuous Sine Wave

This is the traditional type of technology used in most basic detectors. These detectors are also known as VLF (very low frequency) models. While signal processing has improved enormously, the basic way that the signal is sent out and received back hasn't changed a lot. Continuous sine wave detectors create an electro-magnetic field, which is applied to the ground in a continuous wave.

Broad Band Spectrum (BBS) &
Full Band Spectrum (FBS)

This method transmits in multiple frequencies simultaneously instead of just one as with most VLF machines. BBS technology transmits in 17 frequencies (1.5 - 25kHz) simultaneously and FBS transmits in 28 frequencies from 1.5kHz to 100kHz.
This exclusive and patented technology by Minelab has the benefit of offering superior depth and accurate discrimination over a wide variety of targets. Multi-frequency detectors are recognised as the most versatile treasure hunting detectors available on the market today.

VFLEX Technology

This uses state of the art digital and mixed signal components to enhance standard single frequency technology. The advantage of VFLEX technology is that it provides dependable performance and improved immunity to outside interference. VFLEX technology has the added advantage of changing the frequency of the detector by simply changing the coil being used.

Multi-Period Sensing (MPS) &
Dual-Voltage Technology (DVT)

MPS is the exclusive and patented technology that Minelab first introduced in the SD series detectors. Minelab's unique MPS technology transmits a stream of alternating short and long pulses of magnetic field into the ground, causing objects to produce a changed magnetic field of their own. This means that you can locate metal targets at far greater depth than conventional (VLF) detectors, while small targets can still be found in difficult grounds.
MPS technology also aids in the accuracy of ground balance, which limits the number of 'ghost' or false signals.

DVT is a further enhancement on MPS technology that has been incorporated into the GP series detectors including the top of the range GPX-4000. MPS with DVT provides excellent ground cancelling abilities, improved signal-to-noise ratio i.e. very smooth operation with sharp target signals, excellent sensitivity, and depth.

The Three Main Types Of Ground Balance Are:

Manual Ground Balance

Provides the operator with the ability to alter the ground balance to suit various and changing ground mineralisation being detected in.

Automatic Ground Tracking

Minelab first invented true automatic ground balance in 1987 and their world renowned ground tracking circuitry has been a staple technology in their range of detectors since then.
Automatic Ground Tracking refers to the ability of the detector to track changes in ground mineralisation and automatically adjust the ground balance to suit. This ensures perfect ground balance and full detection depth, eliminating the need for the operator to stop and manually adjust the detector as ground conditions change.

Pre-Set Ground Balance

Preset to suit a particular soil type. This limits where the detector is able to be used, but will generally work well in less mineralised sites such as parks, playgrounds and dry beach sand.

What Difference Does Frequency Make?

Measured in kilohertz (kHz), frequency is the number of times a signal is transmitted into the ground and received back per second. The lower the frequency used by the detector, the deeper it can normally penetrate. At low frequencies however, sensitivity to small low conductive target is sometimes reduced. The higher the frequency, the higher the sensitivity to small targets, but it may not penetrate as deeply. In general, gold detectors operate at higher frequencies (to find small nuggets), while coin and treasure detectors work at lower frequencies for deeper penetration.
The exception to this is MPS type metal detectors that are sensitive and deep seeking simultaneously.
^{NOTE: Frequency is only one of the factors that will determine depth andsensitivity, therefore only use it as one of the indicators.}

Types Of Discrimination

Discrimination is the ability of the detector to identify the type of metal object found and to eliminate the unwanted items and indicate only on the desirable ones.

Variable Discrimination

This is the most basic of discrimination types. I t works like a demarcation line in the conductivity level. This level can be set by the operator and all metals with a conductivity lower than where the level is set are eliminated & all metals with a higher conductivity are accepted.

Notch Filter Discrimination

If all metals were arrayed in order of their conductivity, from least conductive to most conductive, Notch Filter discrimination segments that array into "Notches" and each notch or segment can then be accepted or deleted. Depending on the number and width of the notches offered on the model of detector, will determine to some degree how selective the detector can be at eliminating junk from good targets.

2-D Discrimination Or 'SmartFind TM'

Unlike all other detectors on the market, the Minelab Explorer has the ability to test a metal target for two characteristics, its conductivity as well as its ferrous properties.
By testing targets for 2 characteristics, the Explorer is able to see differences in metals that have the same conductivity and eliminate the unwanted trash.

Tone Identification

Some detectors will indicate the possible ID (identity) of a target, by changing the tone of the target signal. Generally low conductive metals will give a lower tone while highly conductive metals will give a higher pitched tone.

Identification Meter

Most coin & treasure detectors today, offer a meter or LCD screen, which will identify the target using either graphic display or numeric numbers.

^{Note: The accuracy of discrimination is dependant on the repeatability of an object's conductivity rating. Man made objects will normally be consistent in their conductivity, however naturally occurring gold nuggets will often have variations in their purity and therefore their conductivity. For this reason, most gold prospecting detectors tend to have more basic discrimination, often only identifying ferrous from non-ferrous objects.}

What Are The Differences Between Coils?

Size

The size of a coil can influence the depth or sensitivity of a detector. The larger the coil, the deeper it tends to detect but it has less sensitivity to tiny targets. The smaller the diameter, the more sensitive it becomes but with less depth.
Smaller coils will also be lighter in weight, easier to control and may be chosen for their ability to negotiate difficult terrain or undergrowth. They are also an advantage in areas of high trash.

Shape

The most common shapes of coils are the conventional solid Round coils, the Elliptical shaped coils and the Open-web coils. The main reason for the change in shape is to conform to a physical requirement, i.e. the elliptical coil can be pushed around bushes or between stony country easier than round coils. Open-web coils help cut through water when detecting in water and are lighter for their size. Conventional round coils are often a more stable and high performing coil and are particularly popular when gold prospecting.

Configuration

A Concentric coil has an inner circle and an outer circle wire winding. Its search pattern is cone shaped and can be useful for accurately pinpointing the target. Concentric coils tend to be noisier in highly mineralised ground and require more over lap of sweep for thorough ground coverage.

Double-D wound coils are the preferred coils for most detecting. They give a blade or chisel shaped signal that covers the ground more uniformly and once an operator becomes accustomed to the signal, pinpointing can be very accurate. Double-D coils are also preferred for their superior ground balancing ability.

Monoloop coils are a special style of coil for MPS technology detectors (SD & GP Series). These coils have one winding of wire around the circumference of the coil and this winding is used to both transmit and receive.
The signal pattern of the Monoloop coil is cone shaped, requiring more over lapping. In extremely heavily mineralised grounds they can be more difficult to ground balance, however they tend to provide slightly better depth than the Double -D coils. Experienced detector operators have always favoured
Monoloop coils. Since the release of the GPX-4000, the features on offer allow the use of Monoloop coils on a wider range of soils.