Does this mean my soil has lots of Iron?

[Sky1]

I started constructing a test bed to determine how my detector will pick up various coins at different depths.

I dug three 5" holes and put a zinc penny, a nickel and a clad dime in one of each holes.

To my surprise the VDI was all over the place, even at only 5 inches they were reading very low and jumpy numbers even the dime.

So I tried another metal detector and got the same results.

Still scratching my head I started checking other places for signals and got an iron hit, started digging, dug a large hole and once the clumps were broken there was no more signal?
Has anyone else had this happen? I am in North Carolina, the soil has a copper color to it.

 

[go-rebels]

Did you "sanitize" the ground before planting the coins by checking the ground in all-metal mode and removing all metal?

What machine are you using? Did you properly ground balance?

Also, you can speed-up the aging of your test bed if you thoroughly water your coins making certain that the ground is saturated to the depth of your targets.

 

[Sky1]

Not sure what you mean by Sanitize, if you mean did I verify there were no signals before I planted the coins then yes, I did.

I believe that the ground in my yard just under the top soil is highly mineralised. I just found a hot rock in another part of my yard. When I go into All Metal mode I notice there is a lot of Iron signals. I am going to dig a few up this weekend to see if they are coming from more of those rocks. I remember the builder said that my house is situated on a lot of bedrock.

Neigher of my detectors can I manually ground balance. One is the Minelab Safari and the other is a Titan 2000 (bounty hunter).

 

[Monte]

I started constructing a test bed to determine how my detector will pick up various coins at different depths ... and ... Not sure what you mean by Sanitize, if you mean did I verify there were no signals before I planted the coins then yes, I did.

Yes, a "test bed" can be useful, but they have their limitations. In this case, it is good that you "sanitized" the test bed area and checked it before planting some test coins. If you had a good ground balances and searched it in an All Metal mode to make sure it was free of any metal target as well as annoying hot rock (or other mineral body), then you're going to be able to "test" your detectors for performance in sites that are equally 'sanitized," or lack any masking target.

I dug three 5" holes and put a zinc penny, a nickel and a clad dime in one of each holes.

Translated, you located over ground that was quite possibly all uniform, such as your yard with soil that was packed or the area was all consistent, and then you selected three spots to disturb the ground and replace it so that you now had three spots that were inconsistent with the surrounding matrix AND had a coin positioned about 5" deep.I am not familiar with the soil that is typical for North Carolin a, but I do know that in many of the ground environments where I live in NW Oregon, and some other western states where I like to hunt, I DO have to deal with higher mineralized ground, and is ground is disturbed, that alone can cause poor performance compared with a long-time compacted soil with positioned coin.

I also know that in the ground environments I usually search, coin-targets can be expected to usually produce a good audio response and associated TID for targets in the surface-to-3"/4" range, and it's not unusual for coins in the 4"/5" range to perhaps 6" to be a little erratic or questionable. Honest 6"-8" deep coins are considered a "deep coin find" even though there might be an occasional coin detected over 8", such as perhaps 9", but that seldom happens.

To my surprise the VDI was all over the place, even at only 5 inches they were reading very low and jumpy numbers even the dime.

I'm not surprised that this happened in freshly disturbed ground with coins planted 5" deep.

I got to thinking that your posts suggest you're new to the hobby so I did a quick scan of some of your posts. It seems you've only been detecting for the past two weeks, and in a reply you made to someone you made the following statement:

It is my understanding that the VDI's and digital functions and rather meaningless if objects are over 3-4" deep. They also slow you down and you need to go by sound.

I think that was your reply to someone made on Nov. 26th or so and it is actually quite correct. The audio response is the #1 indicator you should rely on to find a target, and Target ID info can be inaccurate in many locations, and especially with some larger search coils, for targets located over 3"-4" deep. Then you went and fresh -buried targets at 5" and were surprised you had errant readings?

So I tried another metal detector and got the same results. Neigher of my detectors can I manually ground balance. One is the Minelab Safari and the other is a Titan 2000 (bounty hunter).

Still not too surprised, but then we have to remember that you are new to the hobby and not familiar with metal detectors and proper tuning. Also, it takes time-n-the-field to gain real-life experience on what a detector can and can't do, as you learn all the strengths and weaknesses it might have with various coils, and learn all the adjustment functions.

These are two very different models. I would suspect the Safari to have some form of auto-tracking like the Explorer's, but the Titan 2000 is factory preset.

Still scratching my head I started checking other places for signals and got an iron hit, started digging, dug a large hole and once the clumps were broken there was no more signal?

Has anyone else had this happen? I am in North Carolina, the soil has a copper color to it.

I believe that the ground in my yard just under the top soil is highly mineralized. I just found a hot rock in another part of my yard. When I go into All Metal mode I notice there is a lot of Iron signals. I am going to dig a few up this weekend to see if they are coming from more of those rocks. I remember the builder said that my house is situated on a lot of bedrock.

You didn't mention which detector you were using when you got the "signals from an iron hit" or the mode used, coil used, and settings.

A "hot rock" or a "cold rock" is simply a rock that is out of context with the ground matrix with reference to your detector's ground balance setting. if a detector's ground balance adjustment is set to be 'on" for the general mineralization, then it might respond to a rock or other intense mineral body that is significantly more or less mineralized than the adjacent ground. I have had it happen with rocks, and I have had it happen and demonstrated the annoyance on a few occasions of dense dirt clods in a plowed field.

It depends a lot on the make/model used, the mode you're using, the rejection level if you're in a Discriminate mode, the Ground Balance setting as it relates to the search mode used, and even the search coil to a degree. Quite often, however, you can get an "Iron" hit and dig through some ground and not find anything and it might be a small piece of iron that was located very close to the surface and you are not able to see it if it blends with the disturbed dirt.

Okay, at this point let me just say this:

Welcome to the hobby and the wonderful world of metal detecting. It's a fun outdoor sport that provides us an opportunity to find interesting things, and as we learn and master our detector battery and weed through all the marketing hype that's out there we get to experience the reality of it all.

As for making a "test bed" let me suggest this:

Stomp the ground down firmly where the coins are buried. Soak the area (unless it's as cold as it is here right now) and let that help to get the settling going so that in time, perhaps 6 months to a year, you will have the ground settled and compacted and is a similar state as the surrounding ground matrix. Then you can do a re-test and see how things are working out for you.

In the meantime, there is a whole world of real-life test beds with coins at various depths and angles and in a wide range of ground mineralization, and often with some nearby targets that can mask and alter the "pure" readings you hope to get. So, during the next 6-12 months, just go detecting. Learn what the detector information is in audio and visual response, note the depths and positions of various targets you'll recover. You're just getting your feet wet as you set out to learn the challenges and rewards this hobby provides.

From a guy who isn't a new-comer,

Monte

 

[Sky1]

Wow thanks for the nice clarification Monte. You surely know your stuff!

The hot rock I had and then lost would register a constant low number (9 I think) as I waved it by my coil, it was pretty heavy was thinking it was iron or something. I put it in my jacket pocket and then when I got in the house it was missing so I dropped it somewhere from the backyard to my house. Will probably find it later.

Yeah, when I buried the coins I figured they would vary a bit but on the Bounty Hunter unit the readings went all the way to Iron. With my Safari (forgot the VDI number but suppose it's irrelevant) they gave a wobbly sound.

Maybe for my test bed I can dig a trench and then slant drill horizontally and insert a coin from the side that way so the top soil above the coin is undisturbed, do you think that might work better?

 

[Monte]

Maybe for my test bed I can dig a trench and then slant drill horizontally and insert a coin from the side that way so the top soil above the coin is undisturbed, do you think that might work better?

Sky1, you would still be disturbing the ground adjacent to the "plant" so, depending upon the direction of sweep, it will still cause some issues.

Again, I'd just leave the three coins as they have been planted and refer back to them periodically, like the 1st of each month, and that will give you an idea of how long it might take for the soil compaction to get back in harmony with the adjacent, undisturbed ground. In the meantime, just use the highest level of sensitivity you can w/o chatter or falsing, and keep the rejection low, such as just enough to knock out an iron nail. Then go detecting. Listen to the audio responses first, then refer to any visual information. Pinpoint the target and recover it, making mental notes of how it read and what it turned out to be, the depth, any nearby targets that could mask it, and the ground conditions.

In time it will all start to make sense and you'll get comfortable with target response interpretation.

Happy Hunting,

Monte

 

[UK Brian]

I started this technique for test beds years back and there's no issues if my original instructions are followed which just means not sweeping over the trenched area which should be infilled with the soil removed plus a percentage more creating a raised "bank" (couple of inches minimum). This marks the trench area and by the time the ground has sunk back level the ground effect change becomes not worth worrying about. (Do give the ground a good thump to collapse the soil back down into contact with the coin which is far thinner than the insertion "slot").

The standard test bed used can be much improved upon by having a row of the same type of coin added at increasing depths (I use a pure copper coin buried at five, six, seven up to twelve inches). This is because detection depth is less important than the correct indentification of the item as ferrous/non ferrous. This sort of test bed really opens the eyes to the limitations of metered machines.

 

[go-rebels]

The standard test bed used can be much improved upon by having a row of the same type of coin added at increasing depths (I use a pure copper coin buried at five, six, seven up to twelve inches). This is because detection depth is less important than the correct indentification of the item as ferrous/non ferrous. This sort of test bed really opens the eyes to the limitations of metered machines.

This is very good advice for the construction of the test bed. I use common silver (pre 1965) US dimes buried at 4", 6", 7" & 8" in my test bed. In my dirt the original F75 and Explorer II had a difficult time detecting the 7" and 8" dimes, depending upon ground moisture and EMI. Like Brian said, "This sort of test bed really opens the eyes to the limitations of metered machines".