New Whites PI

[Steve Herschbach]

Hi,

Had to get in on this one.

I'm not so much looking for an alternative to my GPX-4000 as I am for a unit that is better than the Infinium. I liked the Infinium well enough as a general purpose PI unit. I would still be using it for coin and jewelry detecting but for one fact - it suffers immensely from electrical interference. I just got tired of the noise finally and let it go. It has moderate performance compared to a Minelab but is affordable, hip mounts, has waterproof coils, and has a crude discrimination system. I did find quite a few nuggets with the Infinium but was also doing well on coins and jewelry with it and so I guess I'm looking for something more than just a nugget detector. And since other uses invariably mean getting closer to electrical sources I need a quieter unit.

My other complaint on the Infinium is the weight. If you actually want to use the unit underwater (which I did) then the heavy pexiglass case and epoxy filled coils make sense. But they could knock a couple pounds of weight off the unit and probably a couple hundred dollars by putting the unit in a dry land box and using the 10" x 5" DD coil as the stock coil. I came close to puttimg an Infinium in a White's type under arm box with drop in battery pack and the lighter coil. But by trying to serve the dry land market with a dive detector Garrett has made a unit that is heavier and more expensive than need be. If the goal is to serve both markets, make two detectors.

So I can easily be sold a better Infinium type detector. And in fact would have eventually got a GS5 had it not been for the White's and PD rumors. I'm anxiously waiting to get one of each. But the only way I'm ditching my Minelab is if someone can prove beyond a shadow of a doubt that their unit will hit a 1 oz plus nugget at substantially better depth in highly mineralized ground. I'd be more than happy to give up little gold (anything under 1/4 oz) in return and in fact prefer to lose sensitivity to tiny surface steel and iron trash. I've heard various claims that this technically should be no problem. And yet even though the Aussies in particular keep pleading for such a unit, nobody has done it.

So there is the challenge, Reg. Can you tune a detector to hit a relatively solid 2 ounce nugget deeper than a Minelab, regardless of other trade-off?s? I'm talking talking at least a couple inches deeper, not any of this 1/8" deeper stuff.

I'd wish for perfect iron discrimination at full depth, but with all due respects to Dave Emery - I'll believe it when I see it!

Steve Herschbach

[Reg]

Hi Bob,

I wish it was as easy as your choices but it isn't. Now, as for most gold found, you are correct, most is found in less than the first 6 to 8 inches. At least, here in the US it is.

If you read Hakey's recent post on the POZ forum, he indicated he would search and find gold using different coils, then scrape 6" of soil away with a bulldozer and find a lot more large gold, and as he said, "copious amounts" of small gold. Now, remember, he was doing this with a ML. So, the the depth range isn't that far off in OZ either. At least, it isn't in many places.

Here is a link for those interested. In this particular post he didn't discuss his detector but any of you who have followed the Finders forums know the detectors Hakey uses;

http://groups.yahoo.com/group/ProspectinginOz/message/4676

Now, most gold found here in the US is smaller than that found in OZ, i.e. 1/4 oz or less, so focusing on that size gold makes sense. This can be done with a lower powered unit such as the one I use. Now, given the typical size gold found here, I don't lose 30% depth when I compare my low powered unit to any of the ML's. In fact, on most of this gold found I come pretty close to matching the ML for depth and that isn't counting the extremely small gold where my unit clearly beats even the latest model. I do lose some at the 1/4 oz range because of the "hole", but that is being corrected and should be a non issue shortly. Now, I will lose depth if I try to use too big of a coil because that is when my low powered unit doesn't have the oomph.

BTW, some time ago, when Rob and I compared my low powered PI and his 3500, I used a 1/4 oz nugget as the test because I knew it was my worst zone. I wanted to see what the ML would do on it. The ML was superior and actually faired better than I expected, which then made me look into the reasons as to why. I feel I have found at least, some of the reason and am correcting that.

So, this is why I can and do operate my 3 lb low powered detector.

Now, getting back to your choices, I am not sure why you mentioned a 25% loss. There was a loss close to that initially experienced in OZ occurred on testing of very large gold (multi ounce size pieces) at depth. I know of no testing of the typical size gold that we find here. BTW, according to Pennyweight, some recent testing done in the last few days indicated his GS 5 did a decent job even against the new 4000. Since this was public event, I am sure there were a lot of people there.

Here is the link of what he said for those interested;

http://groups.msn.com/GoldDetecting/genera...633912763796061

Now, Pennyweight's unit is a high powered GS 5 unit. From what he says, the 25% difference no longer exists. At least, it doesn't exist on the sizes of gold tested that day.

Reg

[Rattlesnake Jim]

I guess it wouldn't be prudent for them make both, so I would vote for #2 most sensitive with possibility of interference.

[grubstake]

Since I live up here in the motherload, we have cell towers and repeaters, everywhere. and every detector that has been made since the 2200sd has a cancel mode on it. its really not a issue, unless you use a mono coil. even then its not all that bad up here. And there at least 10 towers, and an airport also. The ground is whats bad up here. Rob can tell you, that we have spots up this way that a mono gets really bad in. He had to use my Wallaby coilDD to detect on one patch up here. So i'd rather have one that would run quiet in bad ground with mono coils, and reject iron without kicking gold out. and also one I would not need to run an add on amp on, plenty of volume. Grubstake

[cougar jim]

I would go for the # 2 because the discrimination would eliminate a lot of useless digging.

[Digger Bob]

Guy, please don't read anything into what I say. The questions I asked were theoretical. 25% depth loss in exchange for a more stable machine or good iron ID and less stability with comparable depth. This in no way reflects on what's being developed. Just my own curiosity as to what might most people like if they had a choice.

Eric Foster is the father of Pulse Technology. Bruce Candy and Minelab built on and improved what he came up with. Reg, you have built on that and come up with your own version of a machine that works for you. Hopefully, Whites will build on everyones contributions and add their own tweeks that result in something that fills a niche. Will it be the perfect, everything machine that satisfies everyone? Nope! But I think it will overcome SOME of the problems of all the previous machines out there. That's the hope anyway.

Digger Bob

[Reno Chris]

By far and away, I'd prefer a detector that is the second choice:

"A machine that gets comparable depth to Minelab, is lighter and sturdy with good battery life, but more susceptable to interference. But it has an iron ID that is accurate and reliable to full depth, and compatible with all loops."

I am taking it that you mean interference suseptability about the same as a minelab, but not significanly worse. If you build one that meets that description, I guarentee I'd buy one within the first 6 months it is out on the market. Bob, you detect a lot in the northern Sierras, just as I do, and you know how powerful a detector that could handle the ground mineralization like a PI, and yet descriminate out the iron trash would be. It would have uses in treasure hunting beyond nugget hunting as well.

Chris

[dave wiseman]

What I'm curious about is the amount of gold found by people who have beeped for 10-15 years who now use PI'S against the White's Vlf'S they used back in the day.Granted there was more gold to be found and far less beepers but how would a match up turn out between a PI and VLF with 3 fellows on each side with at least 15 years of experience.Seems like in OZ it's a rare thing to find a VLF gold beeper and yet untold thousands of ounces was found during the 70's,80's,90's with these backward machines.Are the same fellows who raved about the White's years ago finding any more gold than than yesteryear with their PI'S? A beepoff at a neutal site with unknown ground conditions and gold types would be interesting.I realize that every type of detector has it's place and specialty.........Dave

[dave wiseman]

...........And then there's the fellow who found a bucketfull of highgrade out of a quartz vein with a 4000,that his White's couldn't pick up at depth.Don't know the model of the White's.This was at a long closed mine east of Sacramento in the motherlode foothills.............Dave

[FlakMagnet]

Hi Dave,

The 4000 seems to have a much better capability

for being sensitive to gold in quartz.

I wish it could have been you that found the bucket-load...

maybe soon.

All the best,

Flak

[grubstake]

detectors are like wive's, none is perfect, some have flaws, or won't do what you think they will. But if you love them, and take care of them, you can have a lifetime of good times and memories.No one or anything can do it all, some can detect better, or go deeper, or cut out noise. But like a a wise man once said to me, it will do the job. Grubstake

[dave wiseman]

Yeah Flak,that would have been nice.My friend saw the higrade and was stunned by it.I've heard of the fellow and the mine but don't know him personally as that's 80 miles from here.Don't know if he sampled the vein first or not.Gary makes a good point about knowing one's machine and that they all have their uses.Haven't been out in so long my hands turned soft again.............Dave

[Reg]

Hi Steve,

Sorry to take so long to respond to your question.

"Can you tune a detector to hit a relatively solid 2 ounce nugget deeper than a Minelab, regardless of other trade-off?s? I'm talking talking at least a couple inches deeper, not any of this 1/8" deeper stuff."

I am not sure if you are aiming that directly at me or asking a general question as to whether it can be done. So, I will answer it a couple of ways.

The reason for the delay was I was waiting for a response to an email I sent. Unfortunately, I have not received a response which would have helped or could have helped in answering part of your question.

Specifically, as for me, I wouldn't want to tackle trying to build a unit to meet your requirements. Personally, I feel it can be done, but I simply don't have the time or the energy necessary. Right now, I have too many things I am working on, some of which I can't discuss.

Now, if I receive a response from my email, I may be able to discuss in greater detail some things that were revealed to me some time back. All I can say at this time is your target could be well within range based upon some discussions I had via emails some time back.

I find your question intriguing especially after following Hakey's discussions of what he has experienced in OZ. Most of his discussions were on the old Finder's forum but some have shown up on the ProspectinginOZ forum recently.

For those of you who have never heard of Chris Hake, he is one of the very well known OZ prospectors who has found a whole lot of gold with his Minelabs. Because of his extensive experience and the use of a bulldozer to remove a certain amount of topsoil, he has concluded that something strange is happening to the transmit signal. At least it is happening in some areas. Basically, he feels the signal only goes so deep and hits a brick wall type condition and then the signal may go sideways rather than continue down.

This issue was first discussed at length on the old Finders forum a few years ago and has been discussed off and on since then.

Now, if what Chris Hake says is true under all ground conditions, I am not sure your goal could be met. However, I also feel that if this is happening, it basically occurs mainly under certain ground conditions. Unfortunately, such conditions are probably more of a norm in certain areas.

Now, I also believe there are areas where this problem does not occur or doesn't occur as bad. In such areas, then I suspect it is possible to obtain the goal you asked.

If all this sounds confusing, that is because it is. Many years ago, I found somewhat similar limitations as Hakey mentioned when I was using a VLF. Since then, I feel I have seen similar conditions while using a PI.

What is interesting is this concept discussed by Hakey sure blows holes in a lot of statements concerning depth of finds.

So, now that I have made this sort of a riddle, I will say again, I feel your goal can be met, but it would only happen under certain ground conditions.

Reg

[Reg]

Hi All,

Well, this thread has passed the 6000 mark and climbing fast. So, I thought I would toss out some more information to inform some or maybe confuse some who might be interested in what they might expect on the new Whites PI.

No, I have not seen one, but since it has been determined to be based on the GS 5, then I strongly suspect much of what is found on the GS 5 is applicable. So, with that in mind, I will discuss a little more about what I have found out about the GS 5 I have at my house now. Now, keep in mind that I recommended those who might be interested in what to expect should read the GS 5 owners manual.

To begin with, I hope those of you who are following this issue did take time to read the owners manual for the GS 5 because I am going to discuss the high tone, low tone issue at a little depth. The nature of the design of the GS 5 is such that when the detector is fully ground balanced, objects that have a longer decay time than the ground signal will respond with a low tone, commonly referred to as a low also called a "woo" tone. Those objects having a shorter decay time with respond with a high tone also referred to as a"wee" tone.

Now, generally, solid iron objects will respond with a woo or a low tone, as will silver and copper objects such as silver and copper coins. Larger gold can also respond with a low tone. One difference is many iron objects will give a double blip type tone, which makes it possible to distinguish such objects with just a little practice.

Now, the most common size gold we find is generally small, maybe less than 1/4 of an oz. Normally, this size of gold will respond with a high tone. So, a high tone is a good indicator the buried object may be a desirable object.

Ok, just how consistent is this high tone/ low tone feature as it applies to gold? Well, about as consistent as the gold that is tested, if that makes any sense.

What brought this issue to my attention was an exchange of emails with another party on what they assumed to generate a high or a low tone. Their ideas didn't come that close to my ideas on the subject. So, I thought I would check a few nuggets I had to see just what happened.

For starters, I have indicated in the past, the crossover point appeared to be about 1/4 oz when the gold is very solid. So, I thought I would check some of the nuggets around that size and what I found was interesting. As an example, one 3/8 oz nugget gave a weak low tone indicated it was very close to the ground signal setting. Another similar size nugget gave a nice solid high tone. Oops, this nugget didn't quite fit the pattern, so I thought I had better extend the sampling.

Next came checking 3 nice coarse, rough nuggets with some quarts in the nuggets. Well, all of these nuggets are very close to 1/2 oz in weight. All three sounded off with a strong wee signal. Another very solid 1/2 oz nugget generated a very strong low woo tone.

Now, checking a handfull of smaller nuggets, all responded with a decent high or wee tone, except one. That particular nugget hardly responded at all even though it was well over a gram in size. What was wrong with this one particular nugget? I have no idea where I found it so it is hard to say why it acted the way it did, except it was not a solid piece of gold, but quite coarse.

Now, to make this interesting, the information I received via emails indicated some Australian gold changes tone much sooner, in the 4 gram range.

So, what does this all mean? Well, as a general rule of thumb, objects generating a high wee type tone are generally smaller and will not be detected as deep as objects generating a low tone. It also indicates that even some larger gold can fail to generate a low tone. This would also indicate some large gold may not be detected as deep as one might expect. It also indicates there is no clear size or weight of gold that will be at the crossover between the high and low tones.

In other words, this tone stuff can tell us more than we may realize if we let it or it can be confusing. As an example, if we were to find a large specimen that generated a high tone and only had a weak signal, both would indicate the gold isn't one solid mass. So, the high tone basically tells us it is responding much like a small piece of gold. Can this really happen? Of course, if the gold in the mass is a bunch of very small pieces that are not connected or very coarse in nature.

The point being, we can tell a lot more about a target than we realize when we use this tone and learn it well.

Unfortunately, a large percentage of potential owners will most likely not take the time to learn all that it can tell us. If you wonder why I stated what I just did, first answer the question, did you read the owners manual for the GS 5 yet?

BTW, as I mentioned in an earlier post, it would be a good idea to read how a PI works. It sort of helps better understand some of the terms I have mentioned.

Reg

[Reg]

Hi Again,

Well, we are approaching the 6500 view mark so I thought I would expand on this WEE WOO thing. Who knows, maybe we can jump across the 7000 mark shortly.

Now, ML owners know what I am talking when I refer to the WEE WOO subject, because a ML will generally go wee-woo on small gold and woo-wee on larger gold. So, for them, much of what I say makes sense.

For those of you who have never used a ML or a GS 5, but have used a two or three tone discriminating detector, you might be able to relate since most of these discriminating detectors generate a high tone for desirable coins and a low tone for junk.

Well, The GS 5 and the ML do something similar. However, the high tone is caused by objects having a very short time constant such as small gold, lead, or a few other non ferrous objects like some brass shell casings, etc. The woo tone usually indicated a much larger object if it is non ferrous, or it can indicate an iron object.

Now, with that said, and based upon what I mentioned in my previous post, just when a gold object will change from a high tone to a low tone is a lot more complex than simply size or weight.

Fortunately, Eric Foster has done quite a bit of experimenting along these lines and over time he has been nice enough to send me information relating to this condition.

So, I thought I would share some of that information with you. Here is a general quote of some of the things he sent me.

From tests that I have done, nuggets vary a lot in their detectability. The reasons for this can be listed.

Size – Generally, the larger the nugget, the more detectable it is, but it does depend on the following four properties, which can change things dramatically.

Shape – a thin flat nugget can be quite different to a solid nodular nugget of the same weight.

Orientation – nugget that is on edge can also have different detectability to the same one lying flat.

Solidity – a spongey nugget or one made of filaments or interlocking particles will have a different detectability than a similar weight solid one.

Composition – There is considerable variability in the composition of nuggets from different areas, and maybe even from the same area. There only need be a few percent of other metals, usually copper or silver, alloyed with the gold to make it much less detectable. Australian gold is reputed to be purer than that from the US, with gold from the State of Victoria allegedly being the purest of all.

This makes it very difficult to predict the size of nugget on the basis of whether it gives a wee or woo tone on the GS5. I would expect Australian gold to change to a woo tone at a lesser weight than US gold, because of the purity issue.. I have also found that turning a thick flat nugget on its edge, can change the response from a woo to a wee. This is because the eddy current path changes to a different cross section.

All you can really say is that a particular ¼ oz nugget dropped down the response hole, while others of equal weight could give a wee or a woo. Also, if it is Australian gold, then it may be 1/8 oz which does the same. There are just too many variables to give definitive answers.

So, as I mentioned before this WEE WOO thing is much more complex than one might realize. Anyway, it is something to keep in mind whether you are using a ML or a GS 5. I suspect the new Whites will do the same, but that is a guess on my part.

Reg

[kcoulson]

Sounds to me like the only sure thing is to dig it all.

Ken

[Reg]

Hi Ken,

It probably is good idea for a beginner to dig everything so they get a better feel for what the detector is telling them.

With experience and taking a basic course in common sense 101, then a person can apply some of the basics that are built into the design.

Now, I mentioned the iron objects have a tendency to double blip or maybe generate a low high low tone type signal if the iron is solid. Large cans have a tendency to generate a high tone, but will usually cause a response much wider than the coil, while a non ferrous object will cause a much narrower response.

So, operatng with a consistent sweep speed and knowing ones detector, a lot of items can be identified. So, both size and target tone can be used with some consistency. It isn't perfect but it helps.

Normally gold found in an area has certain characteristics. Of course there will be exceptions, but overall, there is some consistency. Now, I mentioned I have 3 different 1/2 oz nuggets that one would think should respond with a low tone, but respond with a high one instead. Since they all look much alike in their general character, I would expect all to react the same. Since I understand the fundamentals of why gold may not follow the general pattern, I don't get too concerned if they don't respond with the tone one might think they should. Actually, I don't get concerned at all. These nuggets came from the Model Creek area and were found within 100 yards of each other.

Now, most of the gold I have found in the Rich Hill area, follows a more traditional pattern I mentioned before, where the 1/4 oz is the size that is the crossover point between the low and high tone. The other half oz nugget I tested did come from that area and respond with a distinct low tone.

So, it is a good idea to know both your detector and what to expect in the area you are hunting if you want to use the tone ID as part of your determination as to dig or not.

Reg

[Reg]

Hi All,

Well we have hit another milestone of over 6800 views on this subject. So, it is time to add some more information I hope you will feel is beneficial. Actually, this info can be applied to all PI’s that have a form of ground balance and not just the GS 5 or the future Whites unit.

BTW, this particular post is quite important in knowing more about PI’s, how they work and why you hear the signals you do.

In this post, I am going to explain more about the “wees and the woos” of the detector world and how they come about in greater detail. This time, I will refer more to my PI because I can do things on it that I can’t do on the GS 5 or on the ML’s. I also I feel it is something that would benefit all PI’s including both the GS 5 and the Whites detector. However, it is my opinion only and based upon my experience in using it.

OK, let’s get started. To begin with, when I refer to the wees and woos, I am referring to the tones you will hear on the detector where a wee is the high tone and the woo is a low tone. On a VLF, if your ground balance is not correct, the detector will sound off with either a positive or a negative audio change as the coil is lowered to the ground. The same holds true for a PI, except with no ground balance signal applied, the audio signal is always positive as the coil is lowered. Also, any target will cause a positive response. So, if you have a PI that has no ground balance, it doesn’t matter what type of rock, metal, etc, it will all sound off with a positive “wee” type signal.

Now, that was simple enough, right.

On a PI, the easiest way to create a form of ground balance is to take an early sample as your target sample and then take a later sample as your ground cancel signal, which I will simply refer to as the GB (ground balance ) signal sample. Now, if you take this GB signal and subtract it from the target signal you will get a reduction in all signals including the ground signal.

If you increase the gain of this GB signal enough you will reach a point where the later GB ground signal equals the ground signal of the main sample and the two cancel. At this point, the ground signal is now ignored and appears to not exist. Once again, there is an amplification of all signals in the GB signal, so there is also a reduction in target responses as well as the ground signal. At this full GB point, it is much like on a VLF where you can bob the coil up and down and here little if any signal at all if there is no target present. This is what I will refer to as the GB point.

So, the GB point equals or is the GB pot setting where the signal from the ground is canceled. For the sake of argument, let’s call this point 100% GB. So, if there is no ground balance signal added, it would be 0% GB.

Now, on a VLF if you add more GB signal than necessary, the ground balance will change quickly and quite noticeably get to a point where, when you lower the coil towards the ground, the audio will shut off or go quiet. You have gone too far at that point. On a PI, it does something very similar but at a much less aggressive rate. However, what will happen on a PI if you go past the 100% GB level is those normally weak positive wee signals that come from basalt just may be now the new GB balance point, so now the basalt or much of it will no longer cause a weak signal but will be canceled. In the mean time, the ground signal will still be almost non existent. If you can here anything at all, it will be a very slight negative response as the coil is lowered towards the ground. Because this signal is so weak, it is really hard to distinguish.

Ok what does all this have to do with the wee or woo stuff? Well, lets go back to the starting point of no or 0% ground balance and take off from there. At the no ground balance position, all target signals are wee’s or high tones. The ground signal will cause a ‘wee’ also. As you could increase the amount of GB signal applied from 0% to 100%, the ground signal would become weaker and weaker, but all signals still remain positive wee responses. Remember, as more and more GB signal is applied so are other negative signals, so all signals are being canceled and not just the ground. In other words, a target signal is also reduced.

Ok, if the overall ground conditions where you are hunting are such that the ground is not a strong response, then much less signal would be required to offset the ground signal to the point it isn’t a problem, and again, all signals are still wee signals. Yes, if you bob the coil up and down rapidly, you will hear some ground signal but normal sweep action will not cause a signal to occur. So, a person could hunt at this point just fine.

Now, we also have some other factor helping with the ground signal elimination. It is commonly called the autotune signal. Because of its design, the autotune feature is trying to adjust for any weak audio threshold change and adjust back to an original setting, so it is somewhat like a mini ground balance setup. Under weak ground conditions, this autotune feature may be all that is needed to eliminate or minimize ground signals.

Getting back to the wees and the woos of the world, once again, all target signals will cause a positive or a wee response at any GB setting before the full GB point. So, even if the ground is very weak in signal, the wees will not covert to woos until the GB control has been turned up to almost the full GB position. Now, just before that magical point is reached, all signals are still wees. Now, at some point we can call the 95% GB, there is enough GB signal to begin to cancel signals that are almost the same time constant as the ground. At this particular point, most objects, including the ground still cause a wee. However, some objects will now cause a woo.

Once we turn the control to the point of 100% or the GB point, then the ground signal no longer causes a response at all. At this point, some objects cause a wee and some objects now cause a woo type signal. Those objects that match the ground will cause no signal and those that have a longer time constant than the ground will now cause a woo type signal. Those objects that have exactly the same signal as the ground will be ignored just as the ground is ignored. Those objects having a time constant shorter than the ground will now generate a “wee” signal. If we adjust the ground balance a little farther, then a greater number of woo’s will be developed indicating that the crossover point is expanded or shifted a little.

Now, since there are certain rocks such as basalt that may still give a positive wee type signal at the 100% range, let’s allow for an extended adjustment to the point where the worst basalt rock is now balanced out. For the sake of argument, let’s say this occurs at the 105% GB point. So, if our GB control will allow adjustments up to the 105% GB range, then we can eliminate basalt signals also.

BTW, I can hear the groans now. What in the world is a time constant, right? Well, I will try to give an explanation in terms that, hopefully, will make it simpler to understand. Let’s say we climb a hill in a car and at the top of the hill, we have different paths to the bottom. Path 1 is a very steep short ramp, path 2 is a longer and less steep ramp and path 3 is even a gentler longer ramp that is a very slight slope and very long run to the bottom. If we were to time how long it takes to get to the bottom on the three paths, path 1 would be fast or short, path 2 would be medium or longer, and path 3 would be the longest and take the most time.

So, if a different car would to head down each ramp and start at the same time, car 1 on path 1 would hit the bottom first, car 2 would be next and car 3 on the longest ramp would take the longest. If this same experiment was to be repeated over and over and each car took the same time, then we could refer to the time of each ramp to be a constant. So, the time constant of the first ramp is short, the time constant of the second ramp is longer, and the time constant of the third ramp is the longest.

Well, here is the beauty of signals in metals or soils. They follow a very similar path as the cars. Inject a signal into a metal and it will take a certain time for that signal to ramp down to no signal. Change metals or composition of a metal, and the ramp time can change. This ramp time is called the time constant.

Now, that was simple enough, wasn’t it? Ok, so most metals, certain ground types, and certain rocks, will create a corresponding voltage ramp signal when subjected to a very strong current pulse and that pulse is shut off quickly. The ramp down time of that signal is the time constant of that signal. Now, if we let the ground signal be the ramp 2, then we will have signals both faster and slower. If we let signals that are faster cause wee signals and signals that are longer, cause woo signals, when we could tell which are longer and which are shorter just by listening to the tone.

Ok, if we take three pieces of the same metal (lets chose gold for the fun of it), but simply change the size of the pieces, then the three will have different time constants also. The small piece will have a short time constant and the largest piece will have the longest. So, knowing this, and using the wee/woo technique where we establish the middle signal to be the null or have the same time constant as the ground, we now know that small pieces are wee’s and large pieces will cause a woo. We also can figure out that one certain size gold is ignored just like the ground.

Hey, this is easy, right?

Here is something interesting, with the exception of some very radical ground, the general setting of the full GB point is always the same regardless of where you are in the world. In other words, the full or the 100% GB point is basically the same between about the worst and the best ground and this holds true around the world. The difference lies in what happens between the no GB and the full GB point. If the ground response is severe, then it may require the GB be turned up to near maximum to eliminate the ground signals enough that one can hunt comfortably.

So, in almost all ground in the world one can set the GB control at the main GB point and most ground ceases to be a problem. Now, allow for a small adjustment on both sides and you are assured of having a ground balance control that works everywhere. This makes it easy to design a ground balance system to a point. What it doesn’t do is allow for the use of less GB in areas where the ground signal is not bad.

Ok how does one tell how bad the ground really is? This is easy on my detector. I can set the ground balance to just the on position and have the gains the same between the target signal and the ground signal channel at that setting. If the ground signal is now a very weak signal, then just turning the GB control up a little more can be enough to basically eliminate the ground signal. Remember, the autotune mentioned earlier? Well, the autotune is always trying to help eliminate or retune to a certain threshold. In areas where the ground signal is weak, this feature and a little GB signal can effectively eliminate the ground signal as a problem. At that point, few if any false signals will occur as the result of the ground itself. In other words, I would have to turn the GB to the normal full GB to get an absolute perfect GB, but because the signal is so weak in some areas, that isn’t necessary.

Now, what does happen when I do this rather than simply turn the control always to the full GB is. because there is less subtract signal used, the actual target signal is stronger than at full GB, but less than if the GB was turned all the way off. So, as we turn up the GB control we also reduce the sensitivity a little because we are subtracting more and more of the target signal right along with the ground signal.

Now, a ML owner may scream and say that this doesn’t happen on their detector. Actually, it does. The reason it is not obvious s simply because the range of ground balance control is very limited, thus making it impossible to really hear any obvious signal reduction changes. The same is done on the present GS 5. On both, the GB adjustment range is very narrow, maybe a range between 95% and 105% as a reference. So, over its range, there is very little difference in the sensitivity of all targets either. There is, however, a large difference between GB off and GB on. This is what GB 5 owners can see when they turn the GB off, and that concerns some of them.

Going back to what I said way at the beginning, my PI is different. On my ground balance adjustment I can adjust from 0 GB to full GB but does it over a very wide range. In other words, I can set it for 10%, 20%, 50% etc. So, I can inject a small amount or a little more, or a little more, etc until I get to the full GB setting. On my unit, I have “wees” for target signals over most of this adjustment. The wee’s and woo’s start at the extreme end of my GB pot adjustment.

Again, on the ML’s and GB 5’s the full pot adjustment range is very limited in its range. It maybe varies from about the 95% point as its minimum to 105% point of the actual GB range. So, they have both wee’s and woo’s all the time. By using a very narrow range, it accomplishes its main goal of ground signal elimination and makes it much easier to make a very fine or precise adjustment. In some aspects it is also less confusing to a novice.

Personally, I prefer my technique which allows me a wide GB adjustment range which I feel expands the ability of the detector because the GB control now becomes a limited range sensitivity control also. It does make it slightly more complicated, but that is easily overcome with some basic use.

So, if there is a full GB adjustment, one can increase the sensitivity indirectly if the ground response is weak. If this can be done, then why not do it? Here in the US, having a much wider GB adjustment does not create a problem. However, in the radical ground found in OZ, it might, so in that case, there may be a need for a coarse and a fine adjustment.

Now the down side of a full range GB control is the fact it does add to the confusion because the woo’s all change to wee’s. In areas where the ground can change radically, it does make it more difficult to adjust. So, the ground signal can cause problems if a person is not familiar enough with their detector may leave the detector adjusted correctly. For someone who used a detector on a daily basis and takes time to fully learn their detector, this probably a non issue. However, for a person who seldom uses their detector, it could cause confusion. So, I do understand why there may be reluctance to the change.

Well, what do you think? Is the information in this post of any value? Does it help clear up some questions of how a PI ground balance works?

Now, one final note, my decision to use an expanded range for my GB control is just one of many decisions that have to be made when determining the final design of a detector. Believe me, there are a lot of similar decisions that are not seen by the person who buys one. They are not as simple to determine just what would be the best design as one might think.

Reg

[bakergeol1]

Reg

Since you have a GS5 in your possession try this trick.

Turn the GB to the 10:00 position. Use an Al pop can and a regular steel can.

All iron here regardless of size and shape will produce a high tone here whereas

gold(roughly above 1/3 ounce) will produce a low tone(also high conductor coins). The Al pop can will of course produce a low tone whereas the steel can a high tone. It would be a method of

distinuishing large gold(above 1/3 oz) from iron of any size. Of course moving the GB beyond

the 12:00 position and the iron will now produce the low tone/double blip.

George

[Reg]

Hi George,

I will try what you have mentioned. I have noticed in the past that you have mentioned other tricks you have learned in regards to the signals on the GS 5, which indicates you have taken the time to learn the different tones and just what occurs at the various settings. Hopefully, you will share more of your knowledge.

I am sure there is a lot more than can be learned about a target once more is known about the signals that occur and when they occur with respect to the adjustment of the ground control.

The adjustment of the GB control moves the setting at which items change from a wee to a woo. Among other things, this is adjusting the level of conductivity that will cause the signal to change. Now, on items such as coins, the setting for each should be a constant, I would think. This is something I need to try. What this implies is something like what you mentioned about the cans. Knowing the right adjustment can help determine one object from another. In this case, it might be able to be used to determine one coin from another.

This also implies that with some work, a basic form of TID might be able to be developed by taking the ratio of the main and GB signal and analyzing it at the various setting. That certainly would be a neat trick if it could be done.

Ironically, something similar is done on a VLF to develop the TID. What many people do not know is the simple fact that TID (target ID) numbers or settings are simply settings indicating the conductivity of the object. Since all coins are made the same, the conductivity will be the same, so they will read the same. That is why they are predictable.

The TID feature on a VLF really does not care if the object is a coin or another piece of metal that has the same conductivity. That is why something like a silver ring can read a perfect dime indication.

Keep in mind that all I am doing is thinking out loud and nothing I have said about being able to provide more info about a target on a PI has been verified yet. So, it is very possible I am wrong. That has happened more than once in my life. (I would think it has been more like a brazilian times.) Now, I have figured out the only way you can do something wrong is to try. It is also the only way to do something right.

Reg

[bakergeol1]

Hi Reg

You can achieve a lot of information in metal ID with a two tone PI such as a GS5 with different GB and pulse delay settings. However, the key like the Infinium is using an elliptical coil and testing toe versus middle of the coil responses. Yes bury all the silver dimes and copper pennies you want and I can distinuish each with ease. However, it is just not practical to remember all of the settings and to apply each of them to the item in question is too time consuming. In addition, advancement of PI technology will probably make 2 tone ID obselete.

George

[Reg]

Hi George,

Thanks for the great ideas. I modified some of the circuitry and found I develop a form of disc level adjustment. It is a crude form of TID that worked quite well for providing a two tone ID for coins. Yes, you can tell some from the others. So, it appears that TID for non ferrous objects is possible. Like all TID's (target ID) it won't be perfect, but it isn't bad.

Obviously, more work has to be done but it does look promising.

This GS 5 is expanding into a very versatile PI. Too bad I didn't try some of these things earlier.

Reg

As an additional note, a quick check in my front yard and I can tell higher conductive coins from most everything else. With an inverting switch like on the newer models, I would have a nice positive signals for the coins and a negative signal for most other items. As it is, the unit I have does not have the switch so I have opposite tones.

My next test is to take it to a park and see how it does there.

[RTP]

Any news on the release date for the new White's yet?

[Steve Herschbach]

Hi Reg,

Thanks for all the thought provoking info!

A couple things. First, my understanding of the Minelab units is that they have two ground balance channels running. An early article by Candy noted that a single ground balance left a "hole" in that a nugget that signaled the same as the ground would be lost. In some way the ground balance point for one channel is different than the other channel, so that nuggets missed by one will be picked up by the other and vice versa.

One channel is the "small nugget" channel and is also the noisier channel. The other channel is the "large nugget" channel and very quiet. Some people run in that channel only in bad ground, although smaller gold will be lost, for quieter operation.

It seems I recall something being said about the "wee" being the response from the one channel and the "woo" the response from the other.

At least that supposedly was the case on the SD units. The GP series eliminated the channel switch and so may operate differently.

This may relate to the new smooth mode in the GPX-4000. Smooth changes the tones. Small items go "wee", middle sized items go "woo", and very large items go "wee" again. This combined with the fact that the smooth mode greatly reduces the response from basalt cobbles would seem to indicate some radical change in the ground balance method being used.

So do you have any thoughts on dual ground balance channels?

I'm in no way an electronics expert and so apologize in advance if I'm way off base on any of the above. Like most here I'm just trying to understand it at all!

Steve Herschbach

[Reg]

Hi Steve,

First, let me say I think I have figured out how to add TID to a PI. The limits are separating thin ferrous objects such as pieces of tin cans from the lower conductive metals such as gold or lead, and I am working on that. The coins should TID quite easily.

Now, your concept of the ML design is about what the patent and articles have said. This concept has been in place even on the SD's. However, the SD's, at least the SD 2100 my dad had, still had a "hole" in the detection zone.

It appears the new GPX has a "hole" also when in the smooth mode. At least that is what was reported by some people testing the new detector in OZ. I suspect if more testing were done, more glitches would show up. Personally, I expected there would be a hole if the machine would ignore basalt and smooth out the ground signal more. I just didn't know what size gold would be involved. This "hole" thing is going to happen no matter who designs it. Basically, it is somewhat like the disc mode on a VLF. Whatever has the same characteristics as that being ignored, will be ignored also.

As for the DT design and trying to fill the hole, I think I have a couple of ideas that work better I plan on implementing when time permits. At the present, I have no hole in my operating design when adjusted to do that. I have been using this design for a while and still have a reasonably smooth GB, but I do introduce sort of a hole of when the GB is extra quiet like when it ignores basalt.

The GS 5 has always had an extra "smooth" GB that eaily ignores basalt when properly adjusted. I suspect the GPX is doing something similar to what the GS 5 is doing to minimize the ground response.

Now, changing the subject back to something you asked a while back about if a detector could be designed that would go deeper by a couple of inches on large nuggets. My response at that time was I was waiting for a response from someone. Well, this someone had mentioned something quite some time back about designing a PI that could detect a quarter size object at a distance of about 3 ft. So, my answer was based upon something told to me by George Payne, who is better known for his contribution in the VLF field.

He had been working on an industrial PI project at the time that had the potential to have exceptional depth. Unfortunately, the project was dropped because it appeared to have some other problems when used in the industrial field. Now, it appears the project will never be built. George keeps saying he is going to write a book on metal detectors. Hopefully, his high powered PI idea will be a chapter in that book. Nw, if we can just get him to write it.

Changing the subject back to this "hole" problem, Eric Foster has been doing some experiments along the lines of just what size gold does get eliminated. Hopefully, he will post hs results at some time in the near future. Some of the results of his testing is extremely interesting to say the least.

Reg