The Cibola Showdown: Test results initiated by JB's response on the "Cibola vs. CZ-5" post

[GT]

JB's last post was excellent and I learned some good things reading the article. Of course being an curious engineer, I decided to run a few tests based on JB's article. The tests are outlined below:

TEST CONDITIONS:

I buried dimes and nickels (both of recent vintage) at different depths in loamy soil that was moist. During the test the soil above and below the coins was well compacted. I ran depth tests using my Cibola and my Minelab Quattro. Both units were optimized to be as sensitive as possible in my soil conditions, the Quattro was ground balanced before each test.

Note: Newly buried coins lack a conductive "halo" layer and will appear smaller in size than older buried coins. With this in mind, older coins should appear as larger targets because they have developed a conductive "halo" and should be detected at greater depths.

OBJECTIVE OF THESE TESTS:
1) Determine if nickels can really be detected deeper than silver coins.
2) Determine which machine detected the "best" during these controlled tests.
3) Determine if the pre-set ground balance circuit of the Cibola took a backseat to the sophisticated auto ground balance circuit of the Quattro.


TEST RESULTS:

CIBOLA test results on a nickel:
I buried a nickel at various depths and the Cibola could accurately detect the nickle at a maximum depth of 7-inches. The nickle was lost at 8-inches and couldn't be detected (not even in Super Tune mode) The Cibola did display one strange affect, when buried at 7-inches the nickel appear as a silver coin and could be detected with the discriminate set at a maximum level.

When a nickle was buried at 6-inches deep. The Cibola could detect it even when 4-inches air gap under the coil. Actual depth was 10-inches (6-inches of soil plus 4 inches of air.) When the nickel was buried at 7-inches the Cibola could not detect the nickel if the air gap between the bottom of the coil and the ground was more than 1/2-inch. The extra inch of soil really tended to dampen the extra lee-way in the air-gap department.

CIBOLA test results on a dime:

The deepest the Cibola could detect a dime was 5-inches. At 6-inches the dime disappears and could not be detected even in Super Tune mode.


QUATTRO test results on a nickel:

The deepest the Quattro could detect a nickle was 7-inches, identical to the Cibola. But at 7-inches it was giving lots of false signals. 75% of the signal were iron signals (negative numbers, no iron was in the soil and no signals were generated when the nickel was removed.)

At 6-inches the Quattro could correctly identify the nickel and consistently give a correct ID number (15 or 16). I was able to still detect the nickel with the coil raised 2-inches off the ground during this test. The total depth was 8-inches (6-inches of soil plus 2-inches of air.) Again during the 7-inch test, I lost the signal if the air-gap was more than 1/2-inch off the ground.


QUATTRO test results on a dime:

Identical to the Cibola results. The deepest the Quattro could detect a dime was 5-inches. No signal appeared at 6-inches. The Quattro threw off false ID numbers about 40% of the time so the reading at 5-inches was kind of iffy.


DISCUSSION and CONCLUSIONS:

CAN NICKELS BE DETECTED DEEPER THAN DIMES?
Yes! The Cibola (and the Quattro which is a multi-frequency system) were both more sensitive on a nickel than a dime. Is this because the nickel is a larger target than the dime OR because the 14kHZ frequency is more sensitive to less conductive metals as outlined in JB's article. I guess my test won't answer the second question.

The only way to tell for sure is to re-test using a silver coin the same size as a nickel (is there such a coin?) But regardless of the detecting mechanism, a nickle is detected at 7-inches and the dime is detected at 5-inches deep.

DOES THE CIBOLA OR QUATTRO DO A BETTER JOB ON NICKELS AND DIMES?
I was really surprised to see the $320 Cibola not only keeping up with the $845 Quattro but actually giving more better signals.

On the test where the nickel was buried 6-inches, the Cibola could detect the coin with an additional 4-inch air gap where the Quattro could only be raised another 2-inches. In this test the Cibola won out.

But the maximum soil depth both machines were about equal. But the Quattro signals were so iffy on the 7-inch nickel test I would have not dug if since I was seeing so many amount of negative numbers coming from the nickel. Even though the Quattro could detect the nickel at 7-inches the results were not acceptable. In this sense the Cibola could accurately see the nickel one inch deeper than the Quattro. The Cibola did think the nickel was a silver coin at 7-inches, but this is acceptable because it would cause me to dig the object.

On the dime, again both machines give the same maximum detection depth but the signal on the Cibola was more assuring because 40% of the time the Quattro would give an incorrect ID number for the dime.

So the answer is yes! The Cibola beats out the Quattro (at least on these tests.)

IS THE AUTO GROUND BALANCE CIRCUIT OF THE QUATTRO SUPERIOR TO THE PRE-SET GROUND CIRCUIT OF THE CIBOLA?
The data speaks for itself. The Cibola with pre-set ground did a better job at giving more reassuring signals than the Quattro at a similar maximum detection depths.

ADDENDUM:

Here is additional information not related to the above tests but is informative nevertheless. While scanning parts of my property I got very strong iron signals in three locations. Both the Cibola and Quattro said iron objects were in the soil. All three times I dug holes 13-inches deep and found no solid iron objects, just rusty looking hardpan clay. The signals disappeared after going down the 13-inches.

This tells me both machines can be fooled by pockets of mineralization. This is interesting in light of the Cibola being a pre-set ground balanced machine and the Quattro being a sophisticated auto tuning machine without improved results.

Last week I was on my friend's property and found that the Cibola does get fooled by rusty bottle caps. The rusty bottle caps sound off as coins. I have a Fisher Excel (out for repair now) that was able to detect the bottle caps pretty readily. So as a side-note, the Fisher Excel does a better job than the Cibola on rusty bottle caps.

 

[Jerry Ga.]

Very interesting comparision GT. I only wish you could do this test with a 1270, X-5 and one of the Nautilus machines (IIb or IIBa) against the Cibola. I predict that the results with the Nauty would be shocking.

 

[GT]

I can only run tests on the machines that I own but if you have these metal detector there's not anything stopping you from running the tests and posting the results.

I encourage others on this forum to compare machines that they own. It's always better to get real data rather than conjecture.

 

[Jerry Ga.]

GT, I agree 100%. I only have one detector at this time (Tejon). I could possibly borrow a machine or two from friends to do controled tests. The results would undoubtably be interesting. Jerry

 

[rentasquid]

Why dont you going out to one of those mineralized pockets and bury the coins there. I would like to hear how they perform under those conditions... How the ground balance (auto or manual) affects the results. I applaude your testing!

Oh, and for a silver coin the size of a nickel, why not use a silver nickel. If my memory is correct, I think that they were made in 1943. I have found a couple of them in the past couple of years. Let me know if you need one. I could send you one if I can find the ones I've dug.

J.

 

[GT]

That's the spirit Jerry!!!

You should get you're friends and yourself together and make it an a weekend occasion! Get some popcorn and rootbeer to enjoy ready to share with your friends after the testing is done! And if you prefer beer to rootbeer make sure to celebrate after the testing phase is over, as drinking beforehand may make your test results null and void.


Find a good spot which tests metal-free beforehand and run some tests with all the detectors. One thing I didn't mention, whenever you run a test make sure you only have one metal detector on a time otherwise the metal detectors may cross-talk in a way that skews your results. Having one metal detector on may make the metal detector under test less responsive.

When I ran my tests I only had one metal detector powered up, the other was off and some distance away from the one I was testing.

Okay Jerry, I'll be watching for your test results!

Take Care,
Gus

 

[GT]

Hi Rentasquid,

If you send me that silver nickel I will definitely run more tests and of course I will return the nickel when I'm finished.

I think many other people in this forum would be interested to know if it is the composition of the nickel or the size of the nickel that the 14kHz frequency is reacting to.

If 14kHz is more sensitive to the less conductive metals like nickel then to silver then the older silver-nickel should be detected at less depth than a modern nickel, or in this case less than 7-inches. However, if it is the size of the coin the 14Hz is reacting to, then the older silver-nickel should be detected at 7-inches deep, which is the same depth as the newer nickel. The third possible outcome would be if the silver-nickel is detected at deeper than 7-inches. This would say that the detector frequency is actually more sensitive to more conductive metals like silver and that people were incorrectly assuming that 14kHz was more sensitive to lower conductive metals.

The only way to know to know for sure is with addtional tests to separate out the two confounding affects, size and composition. So if you have a silver nickel, I'll do the testing.

As far as testing coins out in mineralized soils, I am far more interested in answering the size versus composition question. The tests I ran showed that an auto-ground balance machine (the Quattro) is fooled as easily as a pre-set ground balanced machine (the Cibola) in highly mineralized soil under identical conditions. I guess I could determine if a coin could be detected deeper in mineralized soil with an auto-balancing machine (the Quattro) but to me it doesn't matter since the Cibola seems to do better under normal conditions, the conditions I'd be using it the most in anyway. Now if the Quattro was not fooled by the mineralization, that would be much better because I wouldn't be digging as many false signals. But this was not the case.

I can run this test at a later date but for now I'm interested in characterizing how well these machines do under normal conditions. How would you respond to this question?

Given two metal detectors, metal detector "A" works better under the majority of situations but metal detector "B" can outperform metal detector "A" occassionally under some very extreme conditions. Which detector would you want, if you could only pick one?

Of course I can hear every hardcore detectorist saying they would want both, one for normal conditions and one for extreme conditions.

 

[JB(MS)]

The "silver" nickels are only 35% silver and just a little higher in the conductivity range than standard nickels, not enough difference to make any real difference in results. Try a 90% silver dime versus a normal nickel for more accurate results.

JB

 

[John in Florida]

I would expect both machines to do much better on dimes.

Maybe the dirt needs to be compacted better.


John

 

[GT]

Hi John,

I'm pretty sure the lower than expected depth measurements was because my soil has more minerals than the soil in your area. The soil was compacted well. Even if it wasn't that means there would be more air (porosity in the ground) between the coil and the coin and this would cause increased depth not decreased depth.

How would you characterize the typical soil in your neck of the woods?

 

[GT]

Thanks JB for the statistic on the percentage of silver in the nickel.

Since a dime is smaller than a nickel it would still leave unanswered the question of how much size has to do with detection, even if the dime is 90% silver.

If I ever have enough spare time I may be able to collect similar sized items with different conductivities and run more tests. There's nothing special about a coin, it's still just a piece of metal with a particular shape and conductivity.

 

[John in Florida]

The more air in the ground the less depth. That's why freshly plowed fields are a pain. no depth.

t would be nice to know what area you are in and how high your mineralization is to get an idea of what you max depth would be...


When I had my CZ-5, I would dig a hole 4" wide by 4" deep and put a dime on the bottom and leave the hole incovered. The CZ couldn't see it and it wasn't the mild minera;ization doing it, either.

 

[John in Florida]

The more air in the ground the less depth. That's why freshly plowed fields are a pain. No depth.

It would be nice to know what area you are in and how high your mineralization is in order to get an idea of what your max depth would be...


When I had my CZ-5, I would dig a hole 4" wide by 4" deep and put a dime on the bottom and leave the hole uncovered. The CZ couldn't see it and it wasn't the mild mineralization doing it, either. Just one of those things.

 

[Mike Hillis]

Nickels are larger. Detectable deeper. Dimes are smaller, not as detectable. Plain rule of thumb.

The results match simular tests I have conducted with BH and Tesoro machines. Coins have to have have time to interact with the soil matix. Doesn't matter how compacted the soil is. Only thing that compacting the soil does is mash 7" down to 5" Only way to speed that interaction up that I know of is using salt, and that still takes a month to simulate a long buried coin.

Also, the air gap and depth affects was wonderfully brought out in this test. Just because your long buried 6" dime can be detected with the coil six inchs in the air doesn't mean it can be detected at 12" in the ground.

Great Test GT!!!!

 

[GT]

Hi John,

The CZ-5 sounds like a strange machine. My Cibola sees farther without soil (almost double during an air test.) I always thought that the reason depth decreased in a plowed field was because the "halo" around the buried coin was disrupted by the plowing making the target appear smaller and thus decreasing detection depth?

Anyone else that has more info on this topic can chime in....

 

[GT]

Mike thanks for your input! It's always good to see a fellow detectorists who runs his own tests so he can come to some non-biased conclusions.

There seems to be confusion as to why coins in a plowed field are not detected as deeply as an unplowed field. The reason is the "halo or matrix" around the coin is being disrupted by the plow making the target smaller (Target BEFORE plowing = coin + halo, Target AFTER plowing = coin). A secondary affect is the coin is brought closer the surface, the air interface helps dehydrate any matrix left surrounding the coin. If moisture is missing then the matrix becomes less conductive, again with the affect of making the target appear smaller.

Metal corrosion (metal ions) leaches away from the coin and into the surrounding soil. The mixture of the metallic corrosion, soil, and moisture being the "matrix or halo" This matrix or halo is what makes the metal target appear larger to the metal detector.

The moisture in the ground helps release metallic ions into solution so they can conduct current (Eddie currents being induced by the coil RF). That's why coins can be detected better after a rain or when the ground is wet. Water is required to from the conductive metallic solution which clings around the soil particles around the coin to form the so-called matrix. An analogy, distilled water with no dissolved minerals is a poor conductor but as soon as you add salt (sodium and chlorine ions) it becomes an excellent conductor.

Being an Engineer with a chemistry and earthscience background this stuff is all pretty fundamental to understand. I think most people on these forums have observed these affects (detect deeper in wet ground or not as deep in plowed field) but really don't understand why. You seem to understand this but for those that don't, I hope I've cleared up some mysteries.

 

[Jackpine Savage]

Aaw shucks why not!
Lets have a vote...
All those in favor of the "halo" theory say aye.

All in favor of the moist ground as a better conductor of the transmitted em field and increased sensitivity to the resultant field in the target say.. Amen!

Or vote for sunspots, aurora borealis, sugar highs ect ect..

Tom

 

[Jackpine Savage]

Maybe a function of the way the filters/demodulatars deal with the ground signal??? Heck I don't know.

Gotta go I hear a phone ringing.

Tom

 

[GT]

Playing it safe isn't such a bad thing. But I just had to say what I thougth

 

[BarnacleBill]

Two thoughts to consider:

1. At a saltwater beach, dry sand, single freq high gain machine(Tejon), no problem, rain come, detector go crazy. Dry salt sand vs wet salt sand. Better Auntie Em field?

2. At a saltwater beach, deepest coins I dig with CZ20, some 20+ inches are badly corroded zincs. Half eaten away and leached into a large black spot, with black holes in remainder. And I do this consistently in the winter for some reason, not summer. Now where did I put that zinc voodoo doll?

HH
BarnacleBill