How to Choose the Best Metal Detector for Your Needs

Metal detecting can be divided into two main catergories: Gold Prospecting and Coin and Treasure Hunting, with a sub-division of this, Underwater Detecting. To get the best metal detector for your needs you will firstly have to decide which area most appeals to you.  Once you have decided on how you want to use it, you will be able to buy a highly specialised metal detector with the features you need.

If you plan to go gold detecting and also search for coins and relics with a single metal detector then you must choose carefully, as a coin detectors have difficulty with the minerals found in the gold fields. Like-wise, a gold detectors will not discriminate as accurately as coin & treasure detector will, if at all.  There is therefore a trade off between performance and features and your choice of metal detector should lean towards the area of detecting where you intend to spend most of your time.

During the last few years there have been tremendous advances in metal detector technology. With the use of micro-processors and high-tech surface mount circuitry the metal detector has evolved with greater depth, improved sensitivity, automatic ground balance and superior discrimination. Over the past few years, the Australian company, Minelab Electronics has been one of the most innovative with the invention of a number of new technologies, the most outstanding being the invention of "Multi-Period Sensing" (M.P.S.) as used in the SD & GP gold detector range and "Smart-find" as used in the Explorer. The huge advantage with M.P.S. technology is that it can search far deeper than any other metal detector while still having the sensitivity to equal the best of the high frequency detectors. "Smart-find" discrimination, recently incorporated into their Explorer series, opens up a whole new world of accurately identifying targets.

When checking the different metal detectors, to determine which to buy, there are five main characteristics which can be used to compare one metal detector with another. These are depth, sensitivity, discrimination, ground balance and type of coil. Other factors that should be considered are the size and type of additional coils that are available, how comfortable the detector is to use for long periods of time, what batteries are used, how long they last and of course the price of the detector.

We have prepared this short explanation to try to simplify some of the terminology used by manufacturers with their descriptions so you can better understand some of the differences.

1. DEPTH
This refers to the distance that the metal detector can penetrate and detect metal objects in the ground.  This can be influenced by the frequency the metal detector is operating on (low frequency tends to give better depth than high frequency), how sophisticated it's circuitry is and how well it will cope with highly mineralised soil. Often some metal detectors produce extraordinary depths in air or neutral soil like dry beach sand, but in heavily mineralised gold fields the metal detector becomes noisy and unstable.
 
If you want a metal detector for finding medium to large size objects deep down you should consider a detector operating in a low frequency or one using M.P.S. technology.

2. SENSITIVITY
This is also determined by the frequency the metal detector is operating on.  Some metal detectors are now being manufactured with reasonably high frequency such as 50 and 60 kHz, and this makes them much more sensitive to the small match head size nuggets.  Depth on larger targets often suffers when high frequencies are used.  There are even metal detectors on the market that have two or three frequencies so that you can switch between a low and high frequency depending on what you are looking for and what type of ground you are working in. The Minelab Explorer or Sovereign even operate in several frequencies at the same time maintaining sensitivity and depth. M.P.S. technology, as used in the SD & GP series gold detectors,  likewise gives superior sensitivity and depth simultaneously.

3. DISCRIMINATION
This is the function some metal detectors have that enables the operator to determine what type of metal has been detected before digging it up.  This is a great time saver for treasure hunters, with some discrimination systems being highly accurate.  Notch discrimination enables the operator to segment the items into different categories and "Smart-find" almost fingerprints the target, so that it is highly accurate in its target identification and elimination of junk.  Discrimination is not advised when using the metal detector to search for native gold nuggets, as the impurities in gold and the concentrated minerals in the soil around the nugget will confuse the discriminator and may produce a false reading.  For this reason a lot of metal detectors manufactured specifically for gold prospecting have quite basic discriminators.

4. GROUND BALANCE
For gold prospecting, this is probably the most important function on the metal detector and often the one that is over looked when comparing capabilities of each metal detector. Ground balancing is setting the metal detector so that it can compensate for the effect the minerals in the ground have on the machine.  This allows the gold detector to scan the ground and only give a signal when it passes over a metal object.  If this is not done properly the metal detector will produce false noises from the ground itself and you will find it very difficult to tell the difference between ground noise and a metal target.

All metal detectors come with ground balance of some sort; some can be manually adjusted, some are automatic and some are factory pre-set.  The metal detectors with automatic ground balance excel in highly mineralised soil areas, as their ability to test the ground and compensate every few seconds make them so much easier to use and more efficient.  With manual ground balance it's up to the operator to correctly tune the metal detector to the ground and re-adjust when the ground minerals change.  Metal detectors with pre-set ground balance have been set in the factory for a particular type of ground (normally beach sand or park conditions) and so are ideal for coin and treasure hunting but little use in variable ground conditions like the gold fields.

5. COIL TYPES
Coils come in different shapes, sizes and search patterns.   The common search patterns are Concentric, Double-D and Mono-loop.  The concentric coil gives a cone shape search pattern; very good for pin-pointing but you must overlap each sweep of the coil to maintain a good coverage of the ground.  The concentric coil tends to be more difficult to ground balance so
is therefore more common on coin detectors.  The Double-D search coil gives much better ground coverage and will ground balance more easily than the concentric coil and is the preferred coil on gold prospecting detectors.  The monoloop coil is used in conjunction with the SD & GP detectors allowing greater depth with high sensitivity to small targets.

With regard to coil size, the smaller the coil the more sensitive it should be to tiny targets, and the larger the coil the deeper it should detect medium to large targets.  You can make your metal detector search deeper or detect smaller targets easier by using a range of coil sizes accordingly.

CONCLUSION
In conclusion we would recommend that you consider the main purpose that you want the metal detector for, i.e. gold prospecting or coin and relic hunting and then consider what each machine has to offer for that purpose, and the types of functions important to you.

Ultimately the choice is yours and we hope this information assists you in choosing the right detector for your needs. 

Please feel free to phone us for advice or further information on any detector you have questions about.

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