V3i D2 10" Versus the 950 Concentric

[Elton]

Ok all you seasoned V3i users..What difference will I expect to encounter using the 950 and not the D2 ??

Advantages of D2 ??

Advantages of 950 ???

Why did Whites switch to the 950 other than expense downsize for them on the VX3.???????????

 

[Rob (IL)]

The 10"DD will provide depth similiar to the 950 unless your soil maxtrix is highly mineralized, in which case the 10"DD will outpace the 950 concentric. For me the D2 is deeper.

Pinpointing will be about the same as the 950. The 10"DD will reduce adjacent target masking when compared to the 950 concentric.

Coil types have advantages.

Concentric loops like the 9.5 have the following advantages:

Can get good targets under bad targets because of their cone shaped field
They are 10% quieter regarding magnetic interference from power lines
They have 10% better trash discrimination on iron - steel bottle caps and foil
They can shape the target without walking around it
They pin point accurately

Wide Scan Loops (DD) like the 10D2 have the following advantages:
They have better side by side target separation.
They are more sensitive to smaller than coin size targets.
They are more sensitive off the tip area of the coil.
They smooth out the ground reactivity noise by 10%

 

[5900_XL-1]

Excellent information Rob. I never put a V-rated 950 on the V3i, but I did run the stock 950 on the M6 in "busy" ground in an old park where I had used the V, and had good results there. The DD coils are had to beat on the V3i though. martin

 

[Tim_on_Long_Island]

I use the 950 coil at the beach. The black sand being mineralized, the 950 coil punches through it, better than the D2. I use the D2 in the parks. HH.TIM

 

[Rob (IL)]

Yep Tim I forgot to mention that the 950, or any concentric, is less prone to falsing in the wet at the beach.

 

[Elton]

n/t

 

[Larry (IL)]

Not talked about much is the search pattern advantage of the DD style coils at depth, this factor alone is why I use the DD styled coils. I like to think of a DD coil in three dimensional form where it has not only the back to back or overlapping D shaped coil windings, but it also radiates a big D shaped magnetic field into the ground.

At maximum depth the concentric coils search field is very small due to the cone shape radiation pattern requiring a LOT of overlapping to get good coverage for deep targets. You are probably getting maybe 20% of your coil diameter at maximum depth. The DD coil is more likely retaining 80% of its coils length.

For me, I hunt for deep targets most of the time and I use the SEF 12X10 giving me a search pattern at depth, close to 10 inches per sweep as opposed to a 950 which might be 2 inches per sweep.




A concentric, a DD width pattern and a DD front to back search pattern.
[attachment 274047 DDside.jpg]

 

[Elton]

Just curious about that factor in using a D2 in a trashy park.

 

[Rob (IL)]

Notice Larry's middle picture, there is less junk.

 

[Larry (IL)]

Far less Elton since the search pattern is only 2 inches wide vs. 9.5 inches wide (see image)

 

[Elton]

n/t

 

[JamesBondaka]

In some circumstances...the 950 is good but for all around....I like the D2. Most of the time I use D2 or 4x6 in trash

 

[Elton]

n/t

 

[chopperj]

This thread tells me a lot. I was not aware that the DD coils had this kind of search pattern. This explains why the 4x6 DD shooter is so surgical.

Stupid me didn't know this. Very narrow width, but able to overlap more. Turn 90 degrees and it tells me more.

Now I have a better mental picture of what the coil and V3I are telling me.

 

[Explorer]

I have seen the previously posted diagram many times and don't buy the simplistic stick drawings!
Jeff Foster mapped out the signal strength at various points below the different coil types and illustrates the data in his book "Digging Deeper with the DFX".
I tend to believe his work.

 

[nw1886]

One thing about those "simplistic drawings" though,they very obviously convey enough accuracy to understand general point fast......DD= "Windsheild wiper blade" feild and Concentrics="Inverted traffic cone". Thinking through these two basic concepts will decribe enough to choose the most important advantages for your situation.

About Jeff Foster's book there.
Even though it was written concerning the learning of the DFX, Jeff's style of explanation made the "techie analysis of metal detectors in general" much easier to grow into. For those who do work their way through it's well thought out explanations....it's a reference for products in the industry as a whole. ("Teach a man to fish......and the pole is secondary.") Truly an achievment..

 

[MO-searcher]

Very interesting! The field created by the 950 appears to be shaped more like a dome than a cone. The D2 is a variation of a dome, but narrower at the center.

The narrow field of a DD coil would certainly help in trashy areas and I would think the concentric 950 would do well in open areas and provide better pinpointing.

Thanks for sharing the illustrations, the "cone" and "knife" are easy to visualize and the Jeff Foster diagrams help refine those images.

 

[Rob (IL)]

The forum hasn't heard from Jeff for over a year, maybe two. I guess the book is a no go. It might not help with operation but who knows. Maybe its been all covered already.

[attachment 275384 oldman.gif]

 

[chopperj]

OK... I can buy this. It actually makes more sense. But it does still show a pattern that is narrower than it is long. Good to know.

Thanks

 

[nw1886]

By the time you factor in how you can adjust just how fast one signal is processed (and detector is processing the next), that way simplified explanation has more impact on how the end result works. Not truly accurate....but once you get the feel of a DD, the understanding means a lot using your coil sweeping/making better adjustments as conditions change.

Coils are like potato chips in not being able to have just one. (I remember when I tended to think just having one average coil was good enough....boy has that changed!)