Pulse Induction Training - Wet-Salt

S.A.T. = Self Adjusting Threshold. This is an adjustment that is designed to make the slow/elongated audio responses of the waves, wet-salt, aberrations in (wet) sand bumps, holes in the wet sand.....and the like.,.,.,.,.,., adjustable to where you can tune them out...…. or...….. at minimum...… mitigate these environmental conditions. Speeding up the SAT speed..... would then make these elongated audio responses: 'shorter' in audio length, more tolerable, less interfering, more audibly intelligible. SAT also helps 'maintain' a audio threshold...… for best (read: deeper, more sensitive) performance. On many detectors..... if you permanently engage pinpoint mode.,.,.,.,.,.,., you will notice that the audio threshold 'drifts'...… usually in the direction of 'no audio'...… and ALWAYS in the direction of reduced performance. , . , . , . , . , . , regardless of 'increase or decrease' of the audio threshold.
There is a caveat with 'faster' SAT speeds. A faster SAT speed will desensitize the unit to the shorter audio-length targets...….. which are the diamagnetic conductors. And gold jewelry is diamagnetic. If a target is …… say...….. a gold charm...…… it'll produce a very short audio response (blip) to begin with. Now......speeding up the SAT speed...… worsens the scenario. It makes a ALREADY short audio response...… even shorter.,.,.,.,.,.,.,., to the point of merely a click or tick response...….. or completely nullifies the audio from said diamagnetic target. Use SAT speed Control wisely! A very steady coil sweep-speed.... and superior coil altitude control will (easily) allow you to use a better (slower) SAT speed...… so less diamagnetic targets go "missed".

As of current-day technology; when Pulse Delay is reduced (smaller/lower uS number)….. the more sensitive the P.I. unit will become to smaller targets and lower conductors. But...…. the trade-off is; depth is lost on ring/coin-sized targets (or bigger).

If you are exclusively a "ring" hunter.,.,.,.,., you are missing nearly all of the gold ...on the wet-salt beach. ((( Critical tuition ))).

A whole new (unsuspecting) World will open up...…. the moment a Mfr can create a detector that can start to see/detect tiny and...... especially micro jewelry in a wet-salt environment. (( Just don't hunt a beach that has recently undergone a multi-M$ beach sand replenishment project. TOO much aluminum can-slaw...… rendering your intent: 'useless'. ))



Edited 1 time(s). Last edit at 08/07/2018 02:51AM by NASA-Tom.

"But...…. the trade-off is; depth is lost on ring/coin-sized targets (or bigger). And...…. if you are exclusively a "ring" hunter.,.,.,.,., you are missing nearly all of the gold ...on the wet-salt beach. ((( Critical tuition )))"

Wouldnt this be a reason NOT to have a PI with a very low pulse? Am i misreading this Tom....... are you saying NOW since a majority of the gold found with the VLF machines are rings we are missing alll most all the smaller gold? Or....... if we use a PI and reduce the pulse delay/uS we will start loosing targets on the other end.... like pennies and larger gold? At what point would that shift happen....... say 8uS and we loose class rings, but do we still get the average gold bands in the 5 grams weight. So we start loosing sensitivity..... which means depth to these mid to upper range gold items as well. Take your AquaStar then........ its greatest asset is to small gold? So is this low uS a better choice in the water over a VLF..... or are you saying there is so much more small gold being missed that its worth loosing larger gold?

Dew

Tom’s Aquastar is specially tuned. Here’s what Carl Moreland had to say back in 2012 about short pulse delay’s effects...

Reducing the sample delay increases target response pretty much for ALL targets. It's most noticeable for small gold but everything benefits.

Rick Kempf
Gold Canyon AZ- where there is no gold

lytle78 Wrote:
-------------------------------------------------------
> Tom’s Aquastar is specially tuned. Here’s what Ca
> rl Moreland had to say back in 2012 about short pu
> lse delay’s effects...
>
> Reducing the sample delay increases target resp
> onse pretty much for ALL targets. It's most notice
> able for small gold but everything benefits.


yes, on the manta the gain is verified on all the depth
and on all gold targets, big or small

it is the treatment of the signal and the exceptional silence
which allows this result

to optimize on a target type
(I'm only talking about gold target)

the time of the reading window is more important than the delay
on the first model it is fixed
thereafter, with more digital
we can still optimize the search // large targets or small targets // while staying at the same delay
with pro settings
on a target type give and win a few more centimeters ....

when I say: optimize
I am based on the current manta
which is already above all that we know

so, do not panic
your arms will ask for mercy / before the battery is empty

NASA-Tom Wrote:
-------------------------------------------------------
> Another incremental installment:
>
> In the VLF world...… the smaller the coil,,,, the
> greater the sensitivity to smaller targets. In the
> PI world...….. this is not as pronounced. You can
> run a fairly large coil on a PI unit...and still r
> etain good sensitivity to small targets.
>
> There's always the concern that...….. if you are s
> winging the coil too fast...….. the detector will
> miss targets. In nearly all instances...…. this is
> not the case. If you have a small non-ferrous targ
> et that presents a short audio response to begin w
> ith. , . , . , . , by virtue of swinging the coil
> too fast; you will merely shorten the length of th
> e audio response of that small target...even furth
> er………… whereby YOU (the human) may not detect the
> targets presence; yet, the detector will still det
> ect it. In this case; the targets audio response m
> ay simply sound like a 'click' or 'tick'. . . . .
> . and you may just think it's static......or a tin
> y false audio report.
>
>
> Once iron is 'lit-up'..... it electromagnetically
> decays at a much slower rate. It'll keep 'transmit
> ting' for a long time. Non-ferrous targets (the on
> es we choose to find)…… electromagnetically decay
> at a extremely fast rate..... or..... don't transm
> it at all. Especially diamagnetic materials. (ie:
> gold). Sooooooooo……… when you pass your coil over
> a ferrous BB from an air-rifle...… it may audibly
> sound the size of a (non-ferrous) coin. When you p
> ass your coil over a gold stud earring that is the
> size of a BB...… you may not hear it at all. If yo
> u were to pass your coil over a gold pendant/charm
> (from a necklace) that is the size of 8 or 10 BB's
> laying together...…….. your audio response will be
> very short...… and the detection range (depth) wil
> l be minimal.
>
> Many folks call PI detectors "iron magnets". There
> 's a lot of truth to this...….. as...……. the targe
> ts that PI's find the-most/extremely-readily ….. a
> re ferrous targets. . . . . . . and to tremendous
> depths.
> Ferrous targets = Transmitters
> Non-ferrous targets = Non-Transmitters
>
> In short order...….. you will develop a keen ear t
> o ferrous targets (vs. non-ferrous targets) with a
> Pulse Induction unit. There is a very distinct aud
> io signature to differentiate between the two...…
> that can be learned quickly.
>
> Reducing your Pulse Delay to a faster rate...…… se
> nsitizes the detector to smaller/thinner targets.
>
> If a PI detector allows you to change the Transmit
> pulse length (say from 60uS to 120uS)…….. this doe
> s many things. In general...… it should allow for
> a slightly improved detection of non-Fe targets...
> . a greater detection ability of Fe targets...… a
> greater overall detection depth (but not on a line
> ar scale) of all targets...….. a reduced (1/2-life
> ....in this specific case) battery life . , . , .
> , . , . , . . . . and a host of other things.
>
>
> ((( More to follow...…. if this stuff interests an
> yone. )))

Yes Tom, extremely interesting. I'm soaking up all this great info like a sponge. Thank you, please continue.

Up to my ____ in Pulltabs, Grant

I notice Tom you speak a lot about response...... i think the phones pay a great part in that as well. Nothing worse than a poor pair of phones than respond badly to the targets the machine is picking up. Some machines are doing better with speakers than piezos.

Dew

Dew,

As of current technology PI's...….. as you lower the Pulse Delay...…. there is a increase in Sensitivity to smaller gold targets...…. and a depth increase to large items like gold rings. But...…………. only to a certain point. When Pulse Delay is dropped down to around 11uS (with current-day technology)……. this is (approximately) where maximum depth is achieved... on …….. say...…… a man's gold wedding band. When Pulse Delay is lowered even further...…. say …. down to 9uS...….. very small gold continues to take a boost in detection/performance; yet, a mans gold wedding band will now start to lose some depth/performance. But...….. keep in mind...…….. a gold ring is a continuous closed-circuit loop of continuity.,.,.,.,.,.,.,., which follows different detection principles.
With proper physics & engineering...…. it is entirely possible to run a very low/short Pulse Delay...….. to gain the extra sensitivity/detection of tiny gold...…. AND (via multiple snapshots of/with differing timings) have increased depth/performance on larger items...…. to include continuity loops (rings).
Pulse Delay is one (of many areas/factors) that can help in the detection of smaller gold...…. with depth/sensitivity performance gains.

Yes...… a good set of phones really helps.

So with say the Manta we will gain sensitivity to the smaller gold with the use of the lower pulse delay. Right now most of the pulse water machines are running much higher than the 11uS you mentioned..... around 15 to 24uS i believe. The Finny was closer to that 11uS range........ and was a machine i kind of liked with a good range of coils and things werent all hard wired. So you kind of have to consider the type of gold you want to find and make that delay work for you based on what you know about your beach and where targets tend to end up. Good posts Tom.

When a very concerted effort is being put forth on ""wet-salt & gold jewelry""...…. via time/labor/engineering/resources...… epiphany eye-opener will ensue.

NASA-Tom Wrote:
-------------------------------------------------------
> When a very concerted effort is being put forth on
> ""wet-salt & gold jewelry""...…. via time/labor/en
> gineering/resources...… epiphany eye-opener will e
> nsue.

how about some examples of recent 'eye-opener' finds you've had with PI....

All and all, I've found the very best gold items using my TDI SL. Very smooth running in the wet salt sand, found my very first silver coin on my last beach hunt. Fisher might have a great winner with the Manta, but time will tell. I might note, to me that is what is being promoted here.

PI detectors are “infants” compared to VLF IB detectors. The VLF technologies were developed to more or less a peak more than a decade ago, with many companies seriously spending on further pushing the boundaries of what they were capable of. PI, on the other hand, has lagged. George Overton and Carl Moreland published a book a few years ago called “Inside the Metal Detector”. In it, on page 176 they write...

“Even though pulse induction has been around for 60 years or so, it has been relegated to specialty detectors and has not been explored as deeply as induction balance. There is tremendous room for technological advances, especially in the realm of target identification and discrimination. PI has the ability to detect deeper than IB, so with better ground balance techniques and the addition of discrimination it could easily displace IB as the mainstream technology.”

As far as the notion that this thread is promoting any particular PI machine, I think rather that the whispers of a new entrant into the field of PI beach machines has stimulated Tom to review the state of the art and practice of PI’s in wet salt.

The book by Overton and Moreland is the only technical introduction to metal detectors that I know of and covers all types - with projects included to build your own devices if you wish.

The chapter on PI detectors is especially relevant to this thread and is worth reading in its entirety.

Rick Kempf
Gold Canyon AZ- where there is no gold



Edited 2 time(s). Last edit at 07/05/2018 12:03PM by lytle78.

The timing of the new fisher machine may have inspired Tom to let people know what to expect, what the differences are and encourage tech growth with outside the box thinking. What ever the reason.... im enjoying all the thread. Great to see Tom having/taking the time to do more posting. Threads like these keep the tech people reading and posting here.

Tom, it was mentioned earlier in this thread about a good set of phones, have you found any of the newer offerings from the various mfg's wireless or not to surpass the noise cancel abilities of the Koss that you have used for quite sometime?......to me noise cancel ability is every bit important as the quality of the speakers used in any given set of phones. Not trying to hijack here but when you are looking to distinguish minute tone changes this area could easily be overlooked.

CSH...….. Your wish/quest may come true.

Rick...….. There's a few Mfr's that are putting forth heavy/concerted effort in the P.I. Dept. ------ = Much more than just 'tinkering'.
. Yes...…. the P.I. technology/world is nearly untapped. And with certain/specific new microcontrollers/microprocessors …… we (now) can 'launch'.

Dew...…. Yes...…. as I can see.,.,.,.,., right now..... this thread is hardly prompting any interest with most folks; yet, maybe in the not-so-distant future...…. it'll become more relevant. Sooooooo……. I am TRYING to dedicate 'time' into this thread/project...…. when/while I can. (((By no accident))).

mrb……. Personally...… I do not like/trust wireless phones (yet). The latency issue has (mostly) been resolved; yet/however...… there has been plenty of times whereby the wireless phones were running smoothly/quietly...……….,,,,,,,,,,,,,,,...……….. and a target goes 'audibly unreported'. Problem is: you would never know it! Soooooooooooo…………. I'm not 'sold' on wireless phones (yet). This is ALSO to say...….. I REALLY don't trust 'noise-cancel'.
Recently...….. on one of my aircraft...… I lost an engine 'thrust-bearing'. The low/dull audio 'drowning' from the engine (sounds like a out-of-balance driveshaft on a car)…… my expensive Bose ANR headset ...completely 'noise-cancelled' out this dangerous condition. Luckily ……. I had slid one of the earcups off of my head whilst taxiing ……….. and that is when I heard my dilemma. I would have been MUCH safer/better-off with my $400 old pair of David Clark 13.4's...…. instead of the $1200 deadly technology. Newer/more-expensive/technology..... does not always constitute: "Better".

Tom D. - Lots of interest, but so far, it's another "Wait & See" best seller

Definitely interested to see what it's land based potential may be, will it convert me from a primary relic hunter to a salt water beach hunter? We'll have to "Wait & See".

lytle78 Wrote:
-------------------------------------------------------
> There is tremendous room for tec
> hnological advances, ....

This does not mean that "anything dreamed of" is "therefore possible".

Why do you think that the tremendous advances we've seen in the past 30 to 40 yrs. has occurred ? Why do you think that the same can not be said of pulse vs nails/iron ?

It *is* possible, that no amount of time and dreaming , can make the impossible become true. There are "laws of physics". Not saying I don't dream too. But just saying that to point-to-the-past, and show that something "became true" (ground cancelling disc, heavier than air flight, etc...) does not necessarily equate to: "Therefore, all things are possible".

Some things were merely a function of "faster and smaller" (computers, cell phones, etc....). Other things involve the laws of physics.

TomD - I've not been posting on this thread, but have been watching closely. I'm sure there are others watching and learning like myself. I am tempted to pick up a pulse machine just to learn what they're all about though I'm a good 750 miles to the nearest ocean beach in California.

Rich (Utah)

------------------------------------------------------------------

Just one more good target before I go.



Edited 1 time(s). Last edit at 07/05/2018 11:22PM by Gonebeepin'.

Tom. A guy who has spent the last couple of decades of his life working on how to actually design more effective metal detectors writes “A” and you say essentially that the laws of physics prohibit the progress he is busy working on.

Let me see - do I get convinced by the Engineer/designer or by the neighborhood poo-poo’er. Tom, your caution and soberness is always worth considering, but this time, I’ll go with the guy who has data as opposed to the guy who has only opinions.

Rick Kempf
Gold Canyon AZ- where there is no gold

lytle78 Wrote:
-------------------------------------------------------
> you s
> ay essentially that the laws of physics prohibit t
> he progress

No. Not unless the laws-of-physics allow it. Then in that case, you'd be right .

HA!

The "Laws of Physics" card has been played.

Game over.

Shuffle the deck and deal the cards again and let's see who uses the card next!

Mike Hillis Wrote:
-------------------------------------------------------

>
> The "Laws of Physics" card has been played.
>
> Game over.
>

"Game over" Only when "the card" has been played correctly If it was played incorrectly: I/we are all ears. Eh ?



Edited 1 time(s). Last edit at 07/06/2018 04:39AM by Tom_in_CA.

A slightly different approach.... could change the ballgame.

Location is the key - then the correct tool to unlock it.

None of us really understand much about the movement of gold objects with their very high density to surface area ratio in the sand. The sand itself is moved, sifted, sorted by the tides and waves. We can observe the changing profile of the beach, but can’t see anything below the surface of the sand. We detect and discover targets and form out theories of what is going on, but we know almost nothing certain.

There are some things which are pretty well established. Rings are better targets than other jewelry. Iron debris is a large impediment to gold recovery for PI’s which lack discrimination. Short pulse delays also “light up” small nonferrous targets like split shot, aluminum fragments, etc. Fluffy sand is harder to penetrate than compact sand or crushed shell.

Things which seem less clear are

the degree to which gold objects sink vs. are laterally moved by sand movement.

The actual quantity of gold jewelry of all sizes which remain undiscovered due to depth or masking by ferrous targets - especially the “silent masking” which Tom D. Has described in the past

Whether advanced designs of PI detectors can provide greater depth - not just on rings, but on all gold items while providing useful identification/discrimination of iron

In respect of the last point, the demonstrated ability of ground balancing PI’s to ignore/see through some ferrous targets

New tools with new operating characteristics will likely change how we hunt and the level of target recovery we achieve.

It would be great to see an new “golden age” of beach jewelry recovery. One caution however is that with the shift away from gold rings, etc, this happy fortune of increased recovery might be like nugget hunting with metal detectors was - a boom, followed by increasing scarcity of an non-renewing resource.

Rick Kempf
Gold Canyon AZ- where there is no gold



Edited 1 time(s). Last edit at 07/06/2018 04:07PM by lytle78.

"followed by an increased scarcity of a non-renewing resource".

Sorta like meteorites in Gold Basin,AZ---time was when one could find 10/20 a day,some as big as your fist.Word got out and caravans of hunters descended---today you can hunt for Days and not find a splinter.

One of the neat things about a Pulse Induction unit that allows the user to adjust the 'Pulse Delay'...…. is...….. you can utilize this ability to have another form of ID. For instance...…. if you detect a target that is of …… say...…. medium signal-strength and medium audio-width.,.,.,.,.,.,., you can then reduce or increase the pulse delay...… and acquire (conductive) ID data. If the target is a high conductor (like a coin)...…. signal strength.... and ….audio width.... will only mildly change when you slow-down the Pulse Delay. A low conductor...….. like a gold necklace pendent ……. will 'go away'...… when you slow down Pulse Delay. VERY "telling" data!

Soooooooo………. "Why" can't we do this electronically...…. so the user does not have to!

NASA-Tom Wrote:

> Soooooooo………. "Why" can't we do this electronically
>...…. so the user does not have to!

EXACTLY !! Pulse induction has not changed and there is much to be improved upon.

Up to my ____ in Pulltabs, Grant

I thought this post might inspire more PI information from you Tom....... like how to use all these knobs lol.

[metaldetectingforum.com]

As we (finally) technologically delve into the engineering PI world...…. there's several concerns (advancements) that can be made.


Testing different Pulse Induction detectors in the wet salt environment...… I have noted a unique commonality:

* When reducing the Pulse Delay (on many different flavors of Pulse Induction units)….. the sensitivity to smaller and lower-conductive targets is increased...… as to be expected. BUT...……. each unit has a limitation(s). One unit may present 'best performance' when Pulse Delay is reduced to 17uS. Reducing the Pulse Delay any lower would net no additional gain...…….. and …….. possibly revert to reduced performance. Another unit may authorize 'best performance' when Pulse Delay is reduced down to 10uS. And again...… reducing the Pulse Delay any lower would net no additional gain...…….. and …….. possibly revert to reduced performance. . . . . if Pulse Delay is reduced below 10uS.
Is it the coil that can not handle lower (more precise/stringent requirements) Pulse Delay settings?
Is the receiver getting too close to the transmitter...…. with such short Pulse Delay's?
Do we blame the wet-salt for these limitations. I say 'No' ….. because this restricted performance can be seen/witnessed in a air-test.

Currently...….. I have a Pulse Induction unit that can go down to a 5uS Pulse Delay; yet, anything below 8uS renders no appreciable gain. If we can break this secret code (barrier)……. a paradigm-shift will ensue.

Maybe off topic, but hopefully not too far.

In all other PI machines, the setting is known as Pulse Delay and always identified by micro second numbers.

On the GPX, it is known as Timings, but they don't give us the numbers, just names of the timings. On the newer GPXs, there are new timings to help with smaller gold and for salt. Has anyone been able to break down what pulse delay the GPXs are running? And do the newer timings on the 4800 & 5000 help on the beach? I personally would be afraid to take the GPX onto the beach but I'm sure some have.