Cody's Question - Calling all conductive tone experts

[Charles (Upstate NY)]

Cody asked an excellent question, if ferrous tones seems the obvious best choice (at least to us ferrous fans) then why did Minelab default the tones to conductive?

I don't have an answer but I want one. Perhaps it was because all the older machines based their tones on conductivity e.g. silver high, nickels low and they didn't want to confuse people. Thats a good enough reason but I have often wondered if there wasn't an advantage to using conductive tones over ferrous in terms of improved depth. From time to time the conductive tone camp has suggested as much.

Here's something to think about. Take deeper nickels and indian head cents for example. They can and often do bounce left and right a considerable distance across the ferrous axis thus producing a wide range of tones from low iron to high coin.

Yet its rare that these coins will bounce up and down along the conductive axis. Corrosion may pull them down from their textbook location, heavily warn silver dimes can drop down the conductive axis also. But they don't bounce around. Wouldn't this suggest that the machine has more reliable data on the conductivity of the target than the ferrous content? Or perhaps the ferrous ID is more subject to mineralization and surounding iron.

I'll turn this discussion over to the conductive experts now and listen as I have very little experience with conductive tones.

 

[Chris(SoCenWI)]

n/t

 

[Cody]

There are good reasons for using Ferrous or Conductive. Ferrous is very good for separating iron (ferrous) from nonferrous metals (coins and the like). Discrimination is based on predicted values for different metals so can be drawn as the slope of a right triangle. If the targets we are interested in and the ones we prefer to reject are predicted and plotted then they are the slope.

If Ferrous targets are detected and plotted in comparison to conductive targets we find that ferrous plots can vary as much as 400% from the slope. Conductive plots of the same targets will be extremely close to the slope.

Ferrous is very good for separating metals as far as ferrous and nonferrous is concerned. It is weak when it comes to accuracy. Conductive is conductivity and size so is not conductivity in a pure sense. It is weak in that nails are reported with a high tone and large pieces of metal such as aluminum will be indicated as a silver coin or with a high tone. However, the accuracy is much better than ferrous when compared to predicted values and the ideal slope.

Users will adjust to the sounds they prefer and not notice the differences. What I like to do is use Ferrous sounds as my last menu selection and then simple go to Last and switch to Conductive sounds for comparisons. We don't often associate the differences in tones to the % of difference of ferrous and conductive sounds to the ideal simply because we don't know there is an ideal.

The other reason I think they use conductive is because many users are familiar with that method of presentation. I think that was one problem with the 3D in the tones were changed so pulltabs were raised to a higher pitch and not where people were accustomed to hearing them. You dig more so find more but the tone scale is not what we are use to. I think some other target tones were shifted around so in theory the user could find more older and deeper coins.

So, ferrous is great for separating iron but has a greater percentage of error than conductive and users are familiar with the scale for conductive sounds. These are the reasons why I think conductive is the preset and the sound most used as there are ways to get past iron.

 

[GraveDiggerMax-VaBch-Va]

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[Cody]

I like the Sovereign which uses Conductive sounds. The sounds follow the same general conductive sounds as the Explorer in conductive. I don't think the Excals have ferrous sounds.

Low tones for iron, mid tones for rings, gold, pulltabs, nickels, etc, high tones for copper and silver is the general conductive range.

 

[GraveDiggerMax-VaBch-Va]

n/t

 

[Steve(MS)]

I think both have advantages/disadvantages. Wonder what it would be like to have stereo with one side ferrous and the other side conductivity?
Steve(MS)

 

[AK in KY]

Don't know about anyone else but I think that would push me over the edge as I am close already. HH

AK in KY

 

[Cody]

That is an interesting idea. The Nautilus IIB has discrimination in one ear and all metal in the other. Really great!