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Testing machine

A

Anonymous

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I am trying to test my machine. I seem to find lots of clad, but no really old stuff. I have gone to places where I know there should have been old coins but I have had little to no luck. Thinking it was the operator, I tried a test in my back yard. I dug a 12 inch hold and placed a silver dime in it. My machine did not pick up the coin at all. Next I placed the coin a 8 inches and still did not get a hit. I was surprised. Next, I put a silver quarter in the hole with the same results. What gives here? Is the problem caused because the earch is not packed tightly around the coin? What I am trying to accomplish is to hear the different sounds of the deep coins. Any advise here would be of great benefit. Please advise.
 
Lance,
It might be a good idea to explain how you have your detector set up. This includes such things as threshold, sensitivity, audio gain, deep, fast and masking/discrimination.
Does your setup allow you to detect a penny at 10" in an airtest? Air testing is not generally going to give the same results as a penny in the ground, but if you can not detect a penny at 10" in the air, then something is probably wrong with your setup.
HH,
Glenn
 
Heck might be your settings but even with quickstart and the sensitivity bumped up into the 20's should get good depth on coins buried many years..unfortunately airtesting or testing coins recently buried doesn't produce great depth. Even the factory will tell you under lab conditions 7 inches is good depth. I have no idea how they test. Anyway in the ground at least in my neck of the woods coins buried for years should get them 10 inches plus..and thats where it counts...
 
If there is a lot of clad in your hunting site, you will spend most of your time digging for them. Cherry picking may increase your old finds as a percentage to total. Try to dig stuff half way down the depth gauge or maybe lower than the usual clad find. Pass on most of the shallower finds.
This advice is good for some areas and is not always the way to go.
 
Lance, the EXll is a GREAT machine for old deepies, however, its not as sens. to recently buried stuff like a new test garden. It will however, respond well to old soil with the dirt matrix intact. Keep looking for the older coins and you will find some of em if your patient, one thing that I can tell you is the EXll loves silver!
 
Dan,
I have heard other people make the same comment that the Explorer does not do well in air tests. I would be interested to know what makes people think that. With the sensitivity set to 25, Gain=8 and Deep On, I have detect a penny nicely at 10" in air. That seems quite good to me. What are your thoughts on this?
HH,
Glenn
 
My explorers (XS & II) will not pick up a dime at 10 inches with the stock coil in an air test, with the 15 inch WOT yes but not with the stock coil.
I have found the Explorer really dislikes air between the target and the coil, it goes much deeper through undisturbed soil. See my X1 probe story Sunray posted as as a testimonial for the probe on their website for a prime example of the Explorer losing depth once a hole was dug and a big air space was placed between the coil and the target, in this case both a silver dime and an indian head cent stuck together. They were only about 8 inches down yet there wasn't a peep of a coin signal.
The Explorer doesn't just cancel the ground, it uses it and odd as it might seem ground is better than air when it comes to getting depth. It doesn't much like disturbed soil either.
Settings play a big part in depth also, we'd need a rundown of how you have the machine setup to comment though.
I will give you a suggestion though, next time you go out take an hour and hunt by depth alone, pick a minimum depth below the clad layer, say 6 inches or deeper, run in iron mask -10, and dig every non-iron target that reads 6 inches or deeper. Its a great way to learn a few things about the machine.
 
Charles,
Plese look at my post below to Dan-Pa. I have addressed just the issue you spoke of. I would reallly appreciate your response.
Thanks,
Glenn
 
Captain,
I believe that the explorer air tests well and will never get more depth in the ground (well maybe wet non-mineralized ground) than in the air.
I think this perception comes from many other detectors that do much worse in the ground than they do in the air. Minelab seems to have the best ground compensation circuitry around.
I can usually get a dime at around 8" in the air with the stock. It is pretty much a direct correlation of how high I can run the sensitivity when trying this; keeping in mind that you must be in manual or you never really know where the machine is running at.
What I have found is that in mineralized ground the depth is less, especially in dry conditions. And have also found that the air gap everyone talks about is valid. You really need to be right on the ground to get good depth.
In a pure air test there is no ground and the detector compensates, right on the ground the detector can compensate, but with an air gap and then detecting into ground it does less well. Don't understand the physics here and have not done hugely scientific studies but that sure is my gut perception after a couple hours using the explorer.
Sound familiar?
Chris
 
My machines simply will not hit a penny at 10 inches in an air test, even with my sens at 28 in IM -16. I won't even get a crappy signal let alone a nice one. Are you using normal sounds or 1, 2, or 3? I would be interested in seeing "all" of your settings, a full run down. I'll run some tests with the same and see if anything changes.
 
I won't disagree with your findings however many people including myself have experienced that what was a good solid signal will often up and vanish after one digs a plug. My first conclusion would be that the coin tipped on edge yet I have found some of these deeper in the undisturbed soil beneath my plug so that would seem to suggest an air gap is having a negative effect. I notice the same thing on signals say in the 6 inch range, I should get a good hit on them at 8 inches also but when I raise my coil up a couple inches the signal goes away fast.
This could be more complicated than it first appears and particular to certain soil conditions. If the coil is flat on the ground mostly the machine sees the soil signal. Rais the coil a bit introducing an air/soil mix and perhaps with certain types of soil this fouls up the Explorers ground compensation in a negative way that effects depth?
Just my two cents worth.
 
If you dig a plug and the signal disappears you are probably detecting both air and soil when you swing the coil over. This is where ground compensation seems to suffer. I don't know enough about how the auto ground balance circuits work to have an opinion on why this is so. I wonder if you would still see this phenomenon in neutral soil?
Before I got my periscope I experienced what many complain about, signals disappearing after starting the dig. Now I always know exactly where the target is before I start to dig and never have to recheck the hole. So it's been awhile.
What I do notice is that in taller grass (anytime I can't get right on the ground) and dry mineralized soil that depth seems to suffer. Get a real faint but tasty signal and dig down 3-4 inches to get a wheat or merc. If I was on the deck in wet ground same signal would probably a 6-8" indian or seated. I know in the first case that I'm not holding the coil 3 or 4 inches off the ground; seems that depth suffers by more than the distance the coil is off the ground which suggests to me that the air gap is messing up the ground elimination algorithm.
Does this jive with your findings/gut feelings?
Chris
 
When I have done "air" tests typically I toss a coin on the "ground" and hold the coil up in the air...is that really an air test? No...since the magnetic field extends out a few feet from the coil the ground is still in play. This made me think of something a couple of years back, I was showing my XS to a guy and had the WOT coil on and he wanted to test his wedding band, I had the coil up in the air horizontal to the ground. The guy began waving his ring a LONG way from the coil, I was just about to tell him it won't pick up the ring that far away when to my shock I heard the ring sounding off.
So perhaps we are not comparing apples to apples in that the ground was still part of what I had considered an air test.
 
Charles,
ABOUT THE TECHNIQUE FOR AIR TESTING
After reading the posts below I concluded that everyone does not have the same approach to air testing. When I speak of "air testing" I mean the following:
* I set the detector in a fixed position on a wooden table reasonably far away from any metal objects.
* I then run the target past the bottom side of the coil and measure the distance with a plastic ruler.
* I consider this a real air test because the coil and target are both surrounded by air (as opposed to mineralized or conductive ground beneath the coil).
I see from the posts that many people consider it an air test to lay a target on the ground and run the coil past the target. I have no problem with this definition of an air test, but I can also understand why this would produce different results than the way that I conduct the tests.
THE SETTINGS THAT I USED FOR THE AIR TEST OF THE PENNY
Keep in mind that this does not necessarily represent the settings used for hunting. They are just the settings I used for the air testing. These settings produce a "good" (of course this is relative) response for a 1973 copper penny at 10"
Explorer II settings
Sensitivity= 25
Audio Volume=5
Audio Gain=8
Tone Threshold=5
Tone Variability=10
Tone Limits=10
Sounds=Conduct
Deep=On
Fast=Off
Response=Normal
Iron Mask=-16
* When air testing a penny inside, there may be considerable electrical noise. If there is excessive electrical noise, then setting the mask at -10 may be reduce the noise. I find that either mask setting produces essentially the same results.
A NOTE ABOUT SWEEP SPEED
If one sweeps the target very slowly, then the response becomes somewhat reduced. As one increases the sweep speed, then one hears a "fluted" response. As the sweep speed becomes very fast, then more of a single tone is generated.
A NOTE ABOUT RESPONSE SETTING
Most of my hunting is done with Audio Normal because the other settings tend to drag out the response and makes target separation more difficult.
Most of the air testing is done using Audio Normal. But, I find Audio 1, 2 or 3 will get a more pronounced target response than does Audio Normal.
 
Glenn,
That seems to be another of the explorer myths, that slow is always better. I've found fast gives better depth and more accurate sounds; believe this is what makes the "wiggle" work. Try the same experiment in Auto sensitivity. Found even a more marked difference. If you really creep by the coil you can loose lots of depth.
Anyways the down side is that in high trash areas you really can't use any appreciable speed.
Slow is for target seperation, not depth.
Another small question that I've also heard before. That is increasing iron mask or discrimination to hide electrical noise. I've helped several people with their explorers that couldn't get any depth. One of the main reasons was they had on a ton of discrimination or low IM #s with the sensitivity set way to high. Opening up the screen revealed that the detector was going ape.
The explorer still processes the signals caused by EMI in disc'ed out regions and produces a null, which can cause it to miss targets. I've found the only way to combat this is turn down the sensitivity. Am I missing something here?
Chris
 
It's my understanding that you don't need to use the bottom of the coil. That you can just go over the top and it will be exactly the same in distance and all as the bottom. A lot easier a lot of the time, for a air test. And I have found that correct in the years that I have done it.
 
Charles,
I think that you are correct and it makes little if any difference whether you sweep the target over the bottom or top of the coil. For clarity sake I was just explaining the way I do it.
HH,
Glenn
 
Chris,
I can not speak with any confidence about the subject how discrimination effects depth. Having said that here are some of my thoughts.
DISCRIMINATION TO REDUCE ELECTRICAL NOISE
My thinking is that Noise Cancel should be the first attach on electrical noise. The reason for this thought is that Noise Cancel <STRONG>does not </STRONG>introduce any target discrimination. The noise is cancelled by ignorning frequencies not being transmited by the detector (discriminating out using correlation detecton techniques). The problem is that the Noise Cancel is not 100% effective for broadband noise.
By adding discrimination it may be possible to reduce the noise disturbances. Cody Caldwell has discussed a way to do that using the "Learn" and/or "Edit" feature of the Explorer. I will not rehash those details here.
HOW DISCRIMINATION EFFECTS DEPTH
This is an area where I do not have much actual knowledge. My feeling is that discrimination can not help depth. This means that it is either neutral or degrading to depth performance. My thoughts are (at the risk of stating the obvious):
* For targets that cause the cursor to fall outside the dark region of the Smart screen, then there is little effect of depth. I could be way off base here.
* For targets that fall in the dark region of the screen, then a null is produced.
* For deeper targets, then the target ID ability may be degraded significantly. As a result the cursor may jump around significantly. If the cursor jumps in and out of the dark region of the screen, then there is a good chance that depth performance will be degraded.
HH,
Glenn
 
I figured there must be some factor producing the different results we were seeing. All good info. Also your findings using audio 1 jive with what Beachcomber told me about small gold on the beach, you get a longer signal verses what would be a short blip one might miss on small gold with normal audio.
 
Another thing you can do to combat the EMI is to switch to a smaller coil, smaller coil, smaller antenta.
While not very practical, grounding the Explorer to earth would also quite a lot of the noise. I have my test bench Explorer grounded to earth and can run the sens at 10 indoors and its rock solid steady, remove the ground wire and it goes nuts. Some kind of walking stick with a ground probe on the end might be an interesting experiment at a couple of parks over near Elevatorguy in Boston where big radio antenas give even the X1 probe fits.
 
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