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Coil Tests : Food for Thought

A

Anonymous

Guest
G'day Steve D and All.
I have performed some air-tests also.
All air-tests results were with my SD2000M ("internal sensitivity" modification only)and 12v system. With test coils resting on ground targets were waved above and depths measured from top of coils to bottom of targets.
0.25"(1/4")dia.nugget
4.5 inches with Minelab 11"DD
4.0 inches with Coiltek 14"DD
3.5 inches with Coiltek 18"DD
3.5 inches with Minelab 18"Mono
3.5 inches with Coiltek 24"x12"Mono
1.25"(1 1/4")dia.nugget
11.0 inches with Minelab 11"DD
12.0 inches with Coiltek 14"DD
14.5 1nches with Coiltek 18"DD
15.0 inches with Minelab 18"Mono
15.0 inches with Coiltek 24"x12"Mono
3.5" x 3.5" x 2" native copper piece
20.0 inches with Minelab 11"DD
24.0 inches with Coiltek 14"DD
26.5 1nches with Coiltek 18"DD
28.0 inches with Minelab 18"Mono
26.5 inches with Coiltek 24"x12"Monoes
7" x 6" x 1/4" large thin native copper piece
24.0 inches with Minelab 11"DD
28.0 inches with Coiltek 14"DD
33.5 1nches with Coiltek 18"DD
34.0 inches with Minelab 18"Mono
32.0 inches with Coiltek 24"x12"Monoes
Using the SD's standard 6v system gave on average a 13 - 15 percent drop in air depth but would like to do further tests.
From my results the Minelab 11"DD had the best coil width to depth ratio especially on the largest target as it was able to detect it more than twice its diameter.
More food for thought. Gary Q.
 
HI Garry
Thanks for posting your test results. I will have to drag my results out and do some comparisons. The wife swings a fully modded 2000 but I havent done any comparison tests with it as yet.
What weight were the nuggets used? I consider that the mass is also an important factor in detection depth.
I am also considering a 12v system in the near future
Cheers
Steve D
 
Hi Gary Q
Was the minelab 18" mono the new style or was it the original sd2000 dust bin lid type?
 
Thanks for the feedback Ted & Steve,
Ted the 18"Mono was the original Minelab one,the so called dust bin lid. Its results sure surprised me!
Steve the small nugget mass(0.2 grams) the larger nugget mass(90 gram) mark. The air-depth on the 0.2g was a bit surprising considering its mass.
In regards to the Coiltek 12v system I used, Coiltek says you should notice more depth when useing larger coils but not sure if my air-test results confirm this.
All the best. Gary Q.
 
Thanks Gary
Looks like I'll get the old dust bin lid out next weekend, run 7.3V through it, and take it for a spin.
Ted
 
In example, try a nickle on its side verus laying flat. The mass of the nickle hasn't changed, only the surface area towards the tx/rx is different. HH ps Hope to get down there someday!! Brian
 
I think I heard there was a big variation in performance of the old dust bin lids maybe Gary has a good one.
I have two of them and have never fired them up must do some tests!
regards
kris
 
G'Day Brian and all,
My air-test results would seem to agree with Brian
 
Hi Brian,
Mass does have some effect.If you ground down a nickel to 1/4 of its thickness and laid it flat, it would have the same surface area, but be almost undetectable. Conversely if the nickel was four times as thick, you would get a better range than a standard nickel. You reach a point with increasing mass where there is no improvement and the range may start to decrease. However, this is due to the characteristics of the detector rather than the object.
Eric.
 
I have three, one gram nuggets. One is 22k, one is 20-18k, and one is approximately 10k. I was able to see the 10k the deepest...it is alloyed with copper. The other two appear to be alloyed with silver? All three were "received" at varying depths...which leaves me to beleive that Mr. Foster's post is correct. Purity may play a larger role in detectability than surface area. My best advice for nugget hunters is to use a garden rake if you suspect nuggets a hidden by mineralization. This disrupts the magnetite on the top inches, and presto!!! once hidden nuggets shout out! HH Brian
 
Brian, Your test with the 3 x 1g nuggets has helped to explain why my 1/4"(dia.)0.2g nugget seemed light for its size with good conductivity. I would say its alloyed with copper as I found it and its bigger brother in an area known for copper mining.(where my native copper came from)
Also sounds like my (99%)copper pieces had registed deeper than if made of (99%)gold.
Gary Q.
 
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