Metal Detectors With Reliable Target ID Numbers

[Steve Herschbach]

Which metal detectors have the most reliable target ID numbers?

Target ID is a function of depth - the deeper the target, the more difficult it is to get a clean target ID as the ground signal interferes. Other items directly adjacent to the desired target can also cause inaccurate numbers. The more conductive the item, the higher the resulting ID number, but also the larger the item the higher the number. Silver is more conductive than gold, so a gold item will give a lower number than the same size silver item. But a very large gold item can give a higher number than a small silver item, so numbers do not identify types of metal. Gold and aluminum read the same and vary in size so to dig one you dig the other. Only mass produced items like coins produce numbers that are more or less the same over the years but a zinc penny will read lower than a copper penny due to the change in composition.

In general iron or ferrous targets produce negative numbers or low numbers. Aluminum, gold, and US nickels produce mid-range numbers. And most other US coins produce high numbers. Other countries coins, like Canadian coins with ferrous content, can read all over the place.

The scale applied varies according to manufacturer so the number produced by each detector will vary according to the scale used. The 0-100 range for non-ferrous targets is most common but there are others. Minelab employs a dual number system on a 2D scale with thousands of possible numbers, but they are now normalizing the results produced to conform more closely to the linear scale used by other manufacturers.

White's Visual Discrimination Identification (VDI) Scale

Increasing ground mineralization has a huge effect on the ability to get a good target ID. Ground mineralization is nearly always from iron mineralization, and this tends to make weak targets, whether very small targets or very deep targets, misidentify. The target numbers get dragged lower, and many non-ferrous targets will eventually be identified as iron if buried deep enough. Small non-ferrous readings and iron readings actually overlap. That is why any discrimination at all is particularly risky for gold nugget hunters.

If you want target ID numbers to settle down, lower sensitivity and practice consistent coil control. The target number will often vary depending on how well the target is centered and how fast the coil moves. Perfect ground balance is critical to accurate target id. Outside issues factor in. Electrical interference is a common cause of jumpy target id numbers. In general small coils will often deliver sharper, more consistent target id returns.

Higher sensitivity settings lead to jumpier numbers as the detectors become less stable at higher levels. The interference from the ground signal increases and interference from outside electrical sources also increases, leading to less stable numbers.

Higher frequency detectors are inherently more sensitive and are jumpier. So lean lower frequency for more solid results. Multi frequency detectors act like low frequency detectors and tend to have more solid target numbers due to the ability to analyze a target with different frequencies.

Another issue is the number of target categories, or ID segments, or VDIs, or notches, or bins (all names for the same thing) that a detector offers.

For instance here are the number of possible target id categories or segments each detector below offers:

Fisher CZ-3D = 7

Garrett Ace 250 = 12

Minelab X-Terra 305 = 12

Minelab X-Terra 505 = 19

Minelab X-Terra 705 = 28

Minelab Equinox 800 = 50

Minelab Manticore, Fisher F75 and many other models = 99

White's MXT and many other models = 190

Minelab CTX 3030 = 1750

Fewer target categories means more possible items get lumped together under a single reading, but that the reading is more stable. Many detectors will tell you the difference between a dime and a quarter. The Fisher CZ assumes you want to dig both so puts them under one segment along with most other coins.

People who use detectors with many target numbers usually just watch the numbers jump around and mentally average the results. Some high end detectors can actually do this averaging for you! But I think there is something to be said for owning a detector that simplifies things and offers less possible numbers to start with. The old Fisher CZ method still appeals to me, especially for coin detecting. So do detectors like the Garrett Ace 250 or Minelab X-Terra 505 for the same reason.

The problem is that as people strive to dig deeper targets or smaller targets the numbers will always get less reliable. But if you want to have a quiet performing metal detecting with solid, reliable target numbers look more for coin type detectors running at lower frequencies under 10 kHz or at multiple frequencies and possibly consider getting a detector with fewer possible target segments. And with any detector no matter what just back that sensitivity setting off and you will get more reliable target numbers.

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Detectors often use tones to identify targets and often use far fewer tones than indicated by the possible visual target id numbers. The X-Terra 705 for instance can use 28 tones, one for each segment. However, most people find this too busy, and so simple tone schemes of two, three, or four tones may be selected. I think it is instructive that many people often end up ignoring screen readings and hunting by ear, using just a few tones. This ends up just being an ultra basic target id system much like the simpler units offer. Reality is that most people do not need or care about huge numbers of target numbers. For many just three ranges suffice, low tone for iron, mid tone for most gold items, and high tone for most US coins. The meter could do the same thing, but for marketing purposes more is better and so we get sold on detectors with hundreds of possible target ID numbers. Perhaps this is a digital representation of an old analog meter with its nearly infinite range of response but the reality is we do not need that level of differentiation to make a simple dig or no dig decision.

Finally, a picture often says it all. Below we have a shot of the White's M6 meter. I like it because the decal below illustrates a lot. You see the possible numerical range of -95 to 95 laid out in the middle. Over it is the simplified iron/gold/silver range. Note the slants where they overlap to indicate the readings really do overlap. Then you get the probable target icons. -95 is noted as "hot rock" because many do read there.

The M6 can generate 7 tones depending on the target category. I have added red lines to the image to show where these tones sit in relation to the scale. It breaks down as follows:

-95 = 57 Hz (Very Low) Hot Rock
-94 to -6 = 128 Hz (Low) Iron Junk
-5 to 7 = 145 Hz (Med Low) Gold Earrings, Chains - Foil
8 to 26 = 182 Hz (Medium) Women's Gold Rings/Nickel - Small Pull Tabs
27 to 49 = 259 Hz (Med Hi) Men's Gold Rings - Large Pull Tabs
50 to 70 = 411 Hz (High) Zinc Penny/Indian Head Penny - Screw Caps
71 to 95 = 900 Hz (Very High) Copper Penny/Dime/Quarter/Dollar

Note that the screen reading of +14 is noted as being a nickel or ring but it can also be the "beaver tail" part of an aluminum pull tab or the aluminum ring that holds an eraser on a pencil, among other things.

The best book ever written on the subject of discrimination is "Taking A Closer Look At Metal Detector Discrimination" by Robert C. Brockett. It is out of print but if you find a copy grab it, assuming the topic interests you.

Always remember - when in doubt, dig it out! Your eyes are the best target ID method available.

[fredmason]

Wow, Steve; you sure do a bunch of work and thinking for this forum and all the others you contribute to.

Nice job explaining these various facets of detecting.

I find the higher the sensitivity on my 3030 the jumper it gets;plus many more spurious signals. Also every change in the settings affects the readouts more or less...and finally, my ears tell more than anything else whether I will dig or not. All exactly as you wrote.

thanks

fred

[plidn1]

Great post Steve.

I am new to this forum, but not to detecting. I am primarily a jewelry hunter. 

I Live by the VDI numbers. They are invaluable when you hunt with 0 discrimination. The information contained in those numbers are staggering. Only many, many hours in the field will give you their full benefit.
But they are still, as any type of discriminator, only a guide. There are so many variables on any given day, that nothing is written in stone. 
I use them more to tell me what groups of metals may be tripping the bell at that moment and what I might expect to find when I dig out the target.  

[Steve Herschbach]

Hello plidn1,

Welcome to the forum. Jewelry is my main gig when not nugget detecting as I like gold any way I can find it. There are lots of VDI strategies a person can employ when jewelry detecting. My favorite book on the subject is "DFX Gold Methods" by Clive Clynick. It features the DFX but the methods apply to any target id detector. Just so happens my DFX with Bigfoot coil is my favorite turf jewelry detector but the CTX is catching up.

[Goldguru29]

I am also new to your site. I have a Gold Bug DP and am interested in any information because it came with a small booklet of info. I will be hunting down that book you had mentioned by Mr.Brockett. I just joined a gold prospector club last month because of my detecting intrest. I do thank you for all your effort devoted to this site.

Goldguru

[Steve Herschbach]

Hi Goldguru,

Welcome to the site. Thank you. The truth is the site keeps me from climbing the walls when I am unable to metal detect. If I can't go metal detecting the next best thing is yakking with like minded people about metal detecting!

[~LARGO~]

Steve,

 

Great read!   I intend to try some of your tips.  Especially lowering the sensitivity.

My F75 is a case in point.  Now I am getting somewhat of a handle on this machine, largely because of the tips you shared on using it in the goldfield with success.

 

Thanks for  your very interesting post, and all you do to make our detecting time more enjoyable as well as (hopefully) productive.

 

Gary/Largo

[Steve Herschbach]

Hi Gary,

If there was ever a detector put out that needs a light touch on the sensitivity it is the F75.

I really do not like detectors that are kept "safe" by the manufacturers limiting the sensitivity control. They are the ones you can just run anywhere anytime at max sensitivity. That is like owning a car that you can drive anywhere any time with the pedal floored. Nothing extra, no extra speed, just slow and safe all the time.

The reason manufacturers do that is guess what? You give people a sensitivity control that runs to max and they max it out all the time when they should not. Which leads to complaints of unstable performance and noisy detectors.

The F75 is a machine with all the stops pulled off, so you can run it flat out if conditions allow. But the only time I have ever used mine where that was possible was running all metal mode in rural locations free of electrical interference. All metal mode generally runs smoother and is friendlier to high sensitivity levels.

But get the F75 into town and instead of running at full out 99 sensitivity I am running in disc mode and more like 60-70 on the sensitivity. I seem to have a lot of electrical interference in my local area and the ground is pretty hot in Reno, so the F75 can get pretty chatty if I run the sensitivity too high. And the bottom line is if you experiment with it you only lose little or nothing for depth coming off max sensitivity. Getting rid of all the noise makes it easier to discern real targets, though they may be a bit fainter in response than at higher sensitivity levels.

Another good tip is that smaller coils tend to be quieter and tolerate higher sensitivity levels than large coils.

[~LARGO~]

Hi Steve,
 
A couple of years back, I had borrowed an F75 from a friend, to help me decide if it was a machine that I might be comfortable with, the result was, I found two silver rings as well as some other trinkets. I do have a good range of coils for my F75, a small round, a 9 inch elliptical, as well as a 11 inch dd, which is the stock coil.  Find out how pleasantly easy the F75 was to negotiate, easier than my White's XLT, which I liked very much, I opted to purchase a like new F75 Special Edition.  The machine is so well balanced and screen easy to negotiate in either all metal, or discriminate... Plus it runs for HOURS /up to around 40, or so, on four AA batteries...  Don't you wish the SDC 2300 could do that??
 
I have been trying that new F75 SE a little bit, at a city park near me.There are unforgiving power lines running along the street, so that adjacent lawn near to those power lines very likely don't get hit by higher end detectors, so that area might be a better target for a machine without all the bells and whistles, such as my Troy Shadow with a small coil.  It has a neat and unusual feature, a coin check button, which can tell you with good certainty, if a signal in the coin range is or is not a coin.  So, I will be taking both machines to the park.

 

Sorry for the convoluted subject matter...

 

Gary/Largo

[Rob]

Steve,

 

Really great info! Thanks for posting.

 

Rob