Jul 28, 2006, 03:59 PM
White's VDI list?
I had been a Garrett user for about 10 years, but sold it and bought a White's MXT. I am starting to learn the quirks, but I have two questions?
Is there a nice / detailed list of all metals, etc in the VDI format that is available to study and learn? OR has anyone "mapped" out as much metal as you can?
Why are there negative VDI numbers, what does the negative symbol represent?
Thanks for any input!
Jul 28, 2006, 05:32 PM
Re: White's VDI list?
Hi opacific and welcome to the forum!
I searched for a long time for a nice VDI diagram and could never find one. There is, however, a chart right on the machine (at least for the XLT and DFX).
Basically, the negative end of the VDI spectrum represents magnetic metals and the positive end represents conductive metals. Iron falls into the negative end of the spectrum. A lot of people dig only positive signals. Relic hunters, on the other hand, may want old iron and will dig the negative signals.
VDI's are tricky...the number is generated based on the magnetic and conductive properties of the metal as well as the shape and size of the item. Depth and orientation also play a part. For instance, if you take a small piece of foil it will have a VDI of 5 to 15. If you increase the size of the foil the VDI will increase. So, it's not just the type of metal that is important.
I created a post a while back that dealt with the DFX's different frequency modes (http://forum.treasurenet.com/index.p...c,29656.0.html). If you look at the Best Data column on the spreadsheet you will see the VDI's associated with different items.
Experience, bench-testing, good coil control (ability to ascertain size of object using pinpoint mode, checking target from different directions), reading available books/articles/posts, and getting to know you machine are your best bet to understanding what it's trying to tell you. VDI's are very important for interrogating a target, but it's only a part of the overall picture.
Jul 28, 2006, 05:37 PM
Re: White's VDI list?
Here is a coin list from my library. It is from Art SC from the findmall MXT forum
There is an inherent problem with all VDI numbers in that the deeper you go the more ground mineralzation your detector reads. That is why VDI numbers become unreliable with depth. Gold nugget hunters when detecting at Ganes Creek commonly get a negative number for deep nuggets. Their solution was to dig a little and see if the VDI increases or decreases. If the VDI number increases it is non iron and the target is dug.
SOME VARIOUS COIN VDI’s
Detector: Whites MXT and DFX
Coil: Whites 9.5 Concentric Stock Coil
Coins: Borrowed from friend's coin collection. Each coin sat in a plastic baggie during the test.
Setup: Coins were all resting flat (face up) on the dirt surface of "proven clean" ground with exactly 5” of Telephone books on top of the coin and between the coin and coil.
Actual Readings (Mean or "settled" VDI was used):
94 Dollar, Morgan “Peace”
92 Half Dollar, Franklin
92 Half Dollar, Kennedy, Silver (1964)
91 Half Dollar, Standing Liberty
91 Half Dollar, Kennedy (40% Silver) 1965-1967
90 Half Dollar, Barber
89 Half Dollar, Kennedy, Silver Clad Copper
88-89 Penny, Braided Large Cent (1839-1857)
86 Quarter, Standing Liberty
85 Quarter, Washington, Silver
83 Quarter, Washington, (Clad)
82 Quarter, Barber
80 Dime, Roosevelt, Silver “Rosie”
80 Penny, Draped Bust Cent, (1796-1807)
79 Dime, Roosevelt (Clad)
77 Dime, Mercury
77 Gold Coin, 1 oz.* (* 91% Gold, 3% Silver, & 6% alloy)
76-77 Dime, Barber
75 Two Cent Piece, Tuppence, Bronze (1864-1873)
72-74 Penny, Lincoln, Early Wheat Cent, Copper (1909-195
70-72 Penny, Indian Head Cent (1859-1909)
71-71 Small Cent, Flying Eagle Penny (Copper & Nickel) (1857)
72 Gold Coin, ½ oz.* (* 91% Gold, 3% Silver, & 6% alloy)
52 Gold Coin, ¼ oz.* (* 91% Gold, 3% Silver, & 6% alloy)
26 Gold Coin, 1/10 oz.* (* 91% Gold, 3% Silver, & 6% alloy)
20 Nickel, Jefferson (Modern)
20 Nickel, Victory, "V"
18 Nickel, Early Jefferson
18 Nickel, Buffalo
8-10 Three penny, 3 Cent, Nickel/Copper (1865-1889)
Jul 29, 2006, 12:02 AM
Re: White's VDI list?
Your answer on the MXT site is really all you need. The answers about depth etc. are all correct. The MXT operates differently because it doesn't average but gives a new reading on each sweep. Until you get accustomed to this quirk you may find reading the VDI's difficult. My old whites (analog) needle would lock on dime and stay there until you swept over another target. The MXT will not. Rob
MXT Mr. Bill IDX 5" excelerator 8" excelerator 6x10 DD Blue Max 600 Rat Phones
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