Pulse Induction Training - Wet-Salt

In all of my Decades of hunting beaches with a Pulse Induction (PI) unit ……… there's one very large determinant that justifies (or disqualifies) the selection/utilization of a PI unit. Unsuspectingly...… it is not: "HOW" do I hunt with a PI...…… rather; "WHERE" do I hunt with a PI. "WHERE" is KEY. All too often.... a detectorist purchases a new PI unit and immediately heads to the beach to try it out. First, he'll try it out in the dry sand...…. to immediately realize this is an exercise in futility..... due to the overwhelming amount of targets in the dry sand. The original intent was for the wet sand anyway..... so nothings lost (yet). This is where training/knowledge becomes critical. Up to this point...…. current-day technology PI's (at best) have very poor discrimination abilities …… or none at all. This is to say: You will be digging all ferrous targets...…. and non-ferrous targets. This is where 'time' ……. vs ……. 'ratios'...…... determines whether you will keep/survive with a PI...….. or it ends up in a closet. The key is to hunt areas with the least amount of iron (steel) targets in the sand. Yes, a lot of this can be selected and determined via demographics. In short order, I have learned that you never want to take a PI to a fishing location. If you hunt a beach where fishermen go fishing...….. you will find ferrous fish hooks, fishing lures, fishing leaders...…. and a host of other ferrous fishing related paraphernalia. The percent of ferrous targets..... vs...… non-ferrous targets ….. is greatly increased...……….. to the point of rendering the utilization of a PI unit to: nearly useless/inefficient status. And to hunt a certain beach whereby fishermen AND swimmers go...…….. is still too time-inefficient. Use a PI ONLY in areas where heavy concentrations of SWIMMERS frequent. . . . . . . soooooo many swimmers.... that a fisherman does not have a chance/location to cast a line between all of the swimmers. At these locations …. you will find a lot less ferrous targets on the wet slope......and in the water.

If you live somewhere on planet Earth whereby..... your beaches have black sand; you may have additional justification for the employment of a PI unit.

I have another (self-imposed) rule that determines whether I'll use a PI for the wet-salt beach...…. or select a VLF unit with full ID capabilities. I call it the 40% rule. A PI MUST have an attribute that is (at minimum) 40% greater/better than my best beach hunting VLF ID capable unit. Is the PI 40% more sensitive at finding small & tiny gold..... over my VLF ID unit. Does the PI give 40% greater depth on low conductors..... over my best VLF ID unit.
In order for me to quantify/qualify/justify utilization of a no-ID, all-metal PI unit...….. I have found that a 40% greater gain in one (or more) departments...…… dictates 'time-efficiency' justification. If the PI unit is less than 40% better ...than the VLF unit, I have found that the VLF units ability to ID iron.... makes up for the PI's shortcomings via the time-savings by virtue of NOT digging ferrous targets...…. and finding the non-ferrous targets at a faster rate with a VLF ID-capable unit.

When you hunt with a PI all-metal unit...…… after years of experience...….. you will 'learn-the-language'. A PI has a very discrete, raw-data presentation with every target. There is a audible signature-to-hull-emitter-correlation with each/every target. You can start to 'call' the targets before you dig. Ferromagnetic, Diamagnetic and Paramagnetic targets will be much easier identified...…before you dig...…. with greater experience/skillset. Ferromagnetic targets have a very elongated response. Nails and bobby-pins audibly have a double blip audio response. Small diamagnetic gold targets present a very sharp (almost harsh) discrete audio report.

An All-Metal/Auto-Tune PI unit is a blessing in disguise. With this exact type of configuration...… you can run a very high level of Sensitivity...… to the point of mild threshold instability. Aberrations in the wet-salt sand, bumping into a small seashell, a divot/hole in the wet sand...……… a unsteady sweeping of the coil...…,,,,,,,,,...…… and a host of other things may cause the PI to false; yet, in such a fashion that the audio false is a elongated warble. BUT a small and/or deep target will be a short/sharp/distinct audio report that is much easier discernable over the more broad/elongated falses from all of the said scenarios. With a ID unit (VLF or otherwise)……… falses AND real targets all make a 'beep'...… and are much more difficult to discern...………………….. sooooooooooooooooo …………………….. with a VLF unit; you'll need to turn Sensitivity down to minimize the falsing ….and at the cost of losing depth/sensitivity/performance.

For the next couple of generations of 'mild' ID capable PI units...….. do not get your hopes up too high. A PI's form of ID is quite different from VLF units. Very crude/rudimentary; yet, has some attributes.

Be aware of the tradeoff's with a unit that has user-allowable variable Pulse Delay. If you run your pulse delay at.....say...… 9uS...….. it'll detect small gold much deeper than.....say...….. 15uS. But...……. you will lose depth on higher conductors. ((( To me..... this is an attribute...… as I don't want to dig clad coins on the beach ))).

Also...……….. just because you can detect a (ferromagnetic) staple …. from a regular household stapler..... to tremendous depths.,.,.,.,.,.,., does NOT mean you can detect a small gold stud earring of same size/mass to the same performance levels/depths. In fact, you may be able to detect a staple at great depths..... but can NOT detect a gold stud earring (that is 4-times the mass) at all !!!

For the wet-salt beach...….. I have always felt that a 12" coil is the most nominal/efficient size. Time/size/depth/efficiency/sensitivity.

You need a "Like" button, Tom.

HH
Mike

Interesting-----veeeery interesting.

Agree. Too many jump into a PI and then try to hunt dry beach, fishing spots, or beaches where a vlf is just as deep. Hopefully the manta solves a few of these with the iron disc depending how it works

_________________________________

Nox600, CTX, CZ21, Excal II and White's DF with 920i stealthscoop...I live and hunt at the beach in Wilm NC

Learning the beaches around you makes a huge difference now matter what machine you use. Any given day it could be different ...... so you pick the right beach. Same with a detector. The Xcal isnt a PI...... but for those who have modified it to use it in PP and do reverse disc i think you have some understanding just how much iron is out there on your beach. Who wants to dig it all.... especially during recent drop/active swim periods know whats there? That iron to gold difference can work to your advantage as well. Just no since digging 2 ft with most machines if you are looking for gold.... either you cant PP well or you just want to see whats down there. Digging takes time..... and unnecessary digging is one big time waster....... not to mention hard on the back of us old guys.

Thank you Tom..... very interesting post especially since we are all watching the new Fisher PI. I like that 40% rule....... so true. Like you....... i have no problem NOT finding high conductors.... make my day.

This might be the start of a new page in the book....

No major player in the detector business has tried to market a totally new beach PI since Garrett’s Infinium.

Rick Kempf
Gold Canyon AZ- where there is no gold

motivation is also an important factor in IP hunt
when I'm really motivated,
I take against foot, my usual technique

for example hunt beaches or people does not bathe
9 times out of 10 and even a little more, you can not find anything
and then one day you go out a gold coin to 8000 $ (this one I can not mount it ..)

another example a fishing spot at the bar
there, people bathes too
it was the first time I was on this beach
the sea had done well are working
I never dig so much lead / in 4 days
tides of day and night == motivation !!!!

to finish with 9 rings 8 / 18k and a 9k = 34gr

''the best multifrequency would not get half'' // you will notice again, the number of small rings == 7us == $$$$

motivation is one thing, but equipment is as important
I could not do what I do with a gamate: standard
not solid enough / would not hold a week / to meditate..........



-------------------------------------------------------------------------------
Detector used : Fisher Aquamanta /

Pulsepower Goldscan 5c / Aquastar / Goldquest SSV3 / Nexus Coronado / Vista Gold

Thanks Tom,
I truly appreciate you sharing this with us.
Found it most informative, enlightening and entertaining.
Hopefully there will be more to come.

Up to my ____ in Pulltabs, Grant

Im hoping to read .... and learn a lot about the machine when it comes out from you Tom. If the machine lives up to whats been said.... i dont know how a beach hunter in Fl can do without one. Right now there is only a few inches to be gained with a PI here depending on where it used. This may open up more of those gold targets not seen or deep...... the learning curve, expense, and digging could be worth the lost gold initially.

Great write up Tom! Thanks for posting.

XP Deus
Minelab Etrac
Minelab Equinox 800
Garrett Carrot
22 silvers, 2 silver rings, 1 Gold Ring -YTD 2018


Some of my random digs: [www.youtube.com]

I have to repeat....... i like that 40% rule Tom. You once said....... for the most part we are just gold RING hunting. I have to agree with that....... most of us accept that even thou we dont realize it. On most pages we see RING DADDYS..... or people post how many gold rings they get.... that seems to be the standard. Why? Because thats mostly what we find. Ive used about all the water machines ....... and the gage at the end of the year is just how many gold rings did i find. Is new VLFs increasing finds of OTHER types of gold......... or are they still limited as to what they see and can find.... with the only real advantage being disc? Is a PI with obvious depth over a VLF..... which seems to want to close the gap with some disc and definitely lower Us becoming possibly a better choice? That would change how we judge success as well with smaller gold being found.

There's a TON of intel that goes into a PI. But...….. I would like to see heavy-focus into: Turning the receiver 'on' at 7uS...….. then at 12uS...……. then at 20uS. Then collectively take this data...…… and run it through a comparator ….. for better ID purposes. Pulse(source).....to permeability.....to hysteresis.....to decay-rate...……. for better analyzation datum. (ID)

I think the GPZ-7000 operates on the principle of Constant Current square-wave transmitter...…… and can receive 'sample'...… at any specified selection of timing. This may provide the best possible platform for my (above) quest. The old Fisher Impulse had a very unique way of analyzing...… and could sample/analyze even during the transmit sawtooth/triangle pulse waveform...….. and may also provide a interesting/possible platform basis.... unto which multi-receive samples could be gathered...….. during each periodicity cycle. The critical thing here is...……. small, tiny & micro-jewelry are nearly a pure diamagnetic material...…. whereby zero hysteresis takes place. When the 'source' (xmitted energy) is removed...…. there is no hysteresis (no magnetic memory)...… no energy being retained/ramped-down/decayed/given-off.....for a receiver to 'detect'; hence: "WHY" the bulk of the gold jewelry goes undetected. To have the ability to 'receive sample' DURING the Xmit domain...… is paramount/mandatory for the detection of most gold jewelry. Then...……… sampling AFTER the Xmitter is 'off'...… and at multiple timed samplings...…. would greatly enhance ID. I can also say: wet-salt has a reasonably predictable, 'held-constant' decay ID...……. and anything else (such as gold); has the same AND AND AND yet a different ADDITIONAL signature. And THIS ADDITIONAL signature is 'what' needs to be sensed (detected)….. in order to start to 'see' all of the stuff that we have no idea (can not detect) exists in abundance on the wet-salt beaches. Most gold needs (and can ONLY be detected) when the Xmitter is 'on'.

The above also starts to explain 'why' a tiny piece of iron is HIGHLY detectable..... AND to great depths. The hysteresis of iron is tremendous...……. transmits for a long time....after the source is removed. A small piece of iron...…. versus...….. a small piece of gold .,.,.,.,.,.,.,.,., are two ENTIRELY DIFFERENT animals! The iron will 'transmit/radiate'...….. and for a long time. Gold does not! This is 'why' you can detect a staple from a household stapler to a foot deep!...…. and can NOT detect the same size piece of gold whilst scratching the bottom of the coil with it! The gold does not 'transmit'.

"Knowing the problem"...… is half the solution.
Problem stated!

Well done Tom.

Tom---GREAT info as usual. Really exciting to understand the "inside stuff".

WHAT IF:

I've always wondered if there is a specific Transmitter that LESS affects iron targets (and mineralization). What if...… the Xmitter is of truncated half-sinewave...… or simply full sinewave, sawtooth, triangle, squarewave……… or any other variant. , . , . , . , . , . , that ….. by virtue of non-resonance (or less resonant) to iron targets …….. this would...………… in turn...………………….. give better iron see-thru. Is there something that 'lights-up' non-ferrous targets to a much greater extent...…….. AND/(or)………… hardly lights-up iron. If there is a physics principle that will 'db-down' iron; yet, amp-gain on the non-ferrous targets. (((Or any variant thereof))). I've always looked at PI receivers ….. to do the dirty-work for iron target mitigation; yet, there may be more than one way to desensitize to iron.

And...….. when you turn "On" the Xmitter……. then turn "Off" the Xmitter . , . , . , . , . , . iron lights-up and stays "lit" for a long time...…. even when the transmitter is turned "Off". It takes a long time for iron to ramp-down/stop transmitting-radiating/decay. Is there a way to reduce the amount of iron light-up...….. because...…… it is (unsuspectingly) crippling real-world performance.

NASA-Tom Wrote:
-------------------------------------------------------
> And...….. when you turn "On" the Xmitter……. then t
> urn "Off" the Xmitter . , . , . , . , . , . iron l
> ights-up and stays "lit" for a long time...…. even
> when the transmitter is turned "Off". It takes a l
> ong time for iron to ramp-down/stop transmitting-r
> adiating/decay. Is there a way to reduce the amoun
> t of iron light-up...….. because...…… it is (unsus
> pectingly) crippling real-world performance.


The decay from iron is far greater than non-ferrous which could be easily processed and then when used injunction with a truncated/modified TX sinewave......... This could be a common sense solution to PI target i.d.
If it were taken one step further where a shared and properly micro processed VLF platform was integrated into this architecture..... we might see something on the level of revolutionary.

Up to my ____ in Pulltabs, Grant

Tom, I realize we are talking about this topic in generalized terms but is it possible for a PI detector
to send more than one TX and receive more than one RX simultaneously or via timed intervals, receive, process notch with a narrow band pass for the specific RX return?
Similar to the BBS and FBS that ML uses for VLF but in PI architecture ?

Up to my ____ in Pulltabs, Grant

At the risk of putting everybody who read this to sleep, I have prepared a sort of “blow-by-blow of the 23 minute long beach test in France of the Manta V3 prototype. The production machine from Fisher is expected soon (whatever that means) and the version number of the electronics package is up in the double digits.

Here’s the link again, followed by my timeline and “translation/comments” for the uninterested, this is a good time for a nap.

[m.youtube.com]

Bague OR - gold ring

Tous Metaux - all metal

Discri - discrimination

Discri Coupure du fer - Iron discrim. By silencing

Discri multitons - iron discrim by multitone

0:07 - First test “in the air” Gold Ring - 18K - 2.7 grams - size 11

0:12 - Mode “All Metal”

0:21 - Mode “Discrimination iron cut” - 2 nails (6 cm) crossed

0:29 - Mode “Discrimination multitone” - 2 nails (6 cm) crossed

0:40 - Speed test

0:52 - Second test “in the air” - Iron discrim. By silencing

1:00 - The gold is detected beneath the iron - no discussion of recovery speed (it’s zero)

1:10 - The high tone of gold is heard along with the low sound of iron

1:45 - (my comment) a bag of black volcanic basalt sand from Fuertavantura in the Canary Islands is shown - this has ha high Magnetite content as shown next

Until 2:12 - All Metal - demonstrate all targets including sand react

2:14 - Iron Cut - the ring under the nails responds with normal good tone - the nails and sand are ID’d as ferrous.

2:32 - the sand bag is our over the ring and the ring is still a good strong signal - the nails next to it are ID’s as ferrous

2:54 - the same process in multitone ID

3:01 - a Minelab Soverign is introduced and set up shown

To 3:45 - the Sovereign shows reject of nails and sand bag, acceptance of ring

3:53 - two nails crossed over the ring - no signal

4:17 - the nails removed, the black sand bag put over the ring - weak ironn signal

4:32 - CTX. Introduced and set up shown

To 5:30 - CTX gives iron signal over nails, silent offer sand bag and gives good signal on ring

5:33 - two nails crossed over ring - CTX gives iron signal, then nails removed and black sand placed over ring - no signal

6:20 - bag removed - CTX gives good signal over ring

6:23 - again only iron signal when nails crossed over ring

6:45 - second (larger) bag of volcanic basalt black sand Ron Reunion Island introduced

To 6:54 - the ring is placed ON TOP OF the bag - the CTX gives a weak signal side to side and iron signal front to back - compare this signal to the ring alone (at 5:26 and 6:20)

6:56 - 7:07- the smaller bag is put on top of the ring still resting on the larger bag - CTX gives no signal

7:08 - the Manta in iron cut mode sounds on the ring, weak reaction to small bag on top of large bag of black sand, then hits ring strongly after it is placed on top of the large bag and covered by the small bag

7:52 - 8:15 - the Manta still in iron cut discrimination mode - hits ring strongly under both bags - then “cuts” nails

8.36 - Manta demos recovery speed - ring right next to both bags piled up - perfect signal

9:08 - Manta still in iron cut hits ring under both bags of sand and covered by crossed nails

To 9:53 further demo of iron cut discrim of the sand bags and nails

9:55 - two shallow holes - two nails in one, the ring under 2 nails in the other

10:58 - Manta in all metal sounds off over both covered holes - the nails give a characteristic “double” signal

11:24 - iron cut - nails silent - good signal from ring under nails

11:57 - first small bag of sand over ring - good signal - then large bag - then both bags - same result.

13:56 Gold coin 2 Escudos (about 22 MM - 7 grams) it is buried about 12” deep and is easily detected in iron cut discrimination after demonstrating that there is no other signal in the sand (coin inserted at 15:26)

17:50 - a large gold signet ring 5.7 grams is buried 40 cm (about 16”) it is easily detected in all metal

To 23:10 (end of video) Manta easily hits the ring in both iron cut discrim and multitone discrim.

Rick Kempf
Gold Canyon AZ- where there is no gold

Grant,

Unless I'm unable to make a paradigm-shift...…… right now...….. I see no 'pure' way of doing this (strictly adhering/referring to Pulse Induction definition); yet, many manufacturers have variants/hybrids of the like. Minelab's MPS (Multi Period Sensing) with subsequent multiple pulse timings (differing pulse rates)..... enters into the realm of multi-frequency...…. partially due to the fact that the Xmit signal is not sinusoidal. And to look at a harmonic of the Xmitted freq (like 3rd harmonic)……… as long as there's enough/substantial-remaining energy...…….. this is indeed multi-frequency...….. even though (by definition) only one freq is being transmitted. . . . . and with the utilization of the same coil. I'm quite certain that...… by NOT following the pure/genuine definition of Pulse Induction; rather, employing multiple differing analysis methodology (hybrid)…… is the way to go. If you are using a form of truncated half-sinewave(s)………. and/or multi-frequency half-sinewaves...…. this alone constitutes "multi-frequency". Then...….. to have the demodulators looking at "I" reactive in-phase component...…. and the "Q" resistive component of target response...…. with multiple different sample timings......….all within the receiver; yet, adds more 'receive' intel from the multi-period/freq Xmit side of the house. With today's terminology being heavily convoluted...……. simply means 'hybrid'. . . . . . and we have progressed with 'out-of-the-box' thinking.

NASA-Tom Wrote:
-------------------------------------------------------
> Grant,
>
> Unless I'm unable to make a paradigm-shift...…
> … right now...….. I see no 'pure' way of doing thi
> s (strictly adhering/referring to Pulse Induction
> definition); yet, many manufacturers have variants
> /hybrids of the like. Minelab's MPS (Multi Period
> Sensing) with subsequent multiple pulse timings (
> differing pulse rates)..... enters into the realm
> of multi-frequency...…. partially due to the fact
> that the Xmit signal is not sinusoidal. And to loo
> k at a harmonic of the Xmitted freq (like 3rd harm
> onic)……… as long as there's enough/substantial-rem
> aining energy...…….. this is indeed multi-frequenc
> y...….. even though (by definition) only one freq
> is being transmitted. . . . . and with the utiliza
> tion of the same coil. I'm quite certain that...…
> by NOT following the pure/genuine definition of Pu
> lse Induction; rather, employing multiple differin
> g analysis methodology (hybrid)…… is the way to go
> . If you are using a form of truncated half-sinewa
> ve(s)………. and/or multi-frequency half-sinewaves...
> …. this alone constitutes "multi-frequency". Then
> ...….. to have the demodulators looking at "I" rea
> ctive in-phase component...…. and the "Q" resistiv
> e component of target response...…. with multiple
> different sample timings......….all within the rec
> eiver; yet, adds more 'receive' intel from the mul
> ti-period/freq Xmit side of the house. With today
> 's terminology being heavily convoluted...……. simp
> ly means 'hybrid'. . . . . . and we have progresses
> d with 'out-of-the-box' thinking.


If the decay is analysed from the reactive, resistive, resonate and resonate harmonic Rx return, how is it that someone / anyone has not fine tuned the Rx side to accurately extrapolate these results into a decay time gradient for the purpose of I.D. ?
Is the decay rate of both ferrous and nonferrous metals so close that it is indistinguishable ???
I realize the variables of salinity, moisture content, mineralization etc etc will affect both the depth of both the TX and the RX but lets leave that aside for this moment.

Is there a possibility that with some of this technology utilizing a 3rd harmonic, be expanded upon ? Is the decay rate of all or most ferrous and nonferrous metals long enough to accurately read/analyze a 4th or 5th harmonic ? Would this additional sampling be beneficial ?
Would a gold ring VS aluminum square tab VS a bobby pin have differential characteristics that are not being sampled that could be ? Everything in the universe has a specific ________.

I'm just rambling on blindly throwing darts at this board but with this type of wandering, an epiphany sometimes rears its head.
I'm still not understanding how this technology has not advanced further.

Up to my ____ in Pulltabs, Grant



Edited 1 time(s). Last edit at 06/20/2018 01:58AM by Up to my ____ in Pulltabs, Grant.

Yes, there is a tremendous difference (and measurable) when you 'light-up' a Fe target...….. versus...….. a non-Fe target. And with faster clock-speed microcontrollers/microprocessors of today...…… it is highly differentiable.

Fisher put some 'time/money' into the Fisher Impulse 30 years ago. Minelab has (and continues) to sink time/resources/money into PI technology. Eric Foster hit a grand-slam/home-run with his 25 year old AquaStar (and subsequent Gold Scan-5). The White's TDI is a 'mass-produced' Gold Scan-5. And the AS, GS-5 & TDI are of the old/standard Continuous Current based transmitter...…… which is far from multi-freq...……. AND...……. only "receives" AFTER the transmitter is turned off. The highly-tuned hand-made coils of the AquaStar & Gold Scan-5 is what allowed for Pulse Delay analyzation …. to go below 12uS. My particular AquaStar can go down to approx. 8.8uS. This allows for more sensitivity/detection of some gold jewelry; yet, most gold jewelry still goes undetected. (((When you turn the receiver "On" AFTER the gold targets are no longer radiating/transmitting...…. you will never detect/see them; hence, most gold goes undetected))).

When a PI turns "On" the receiver after the transmitter is "Off"...….. this is also AFTER most gold jewelry stops radiating/transmitting.,.,.,.,.,.,.,.,.,. … the gold will go 'missed'.
A VLF metal detector operates on the principle of Xmitting & Rcving continuously. This is to say...…. the receiver is "On" all of the time.....,,,,,, and the transmitter is also "On" all of the time. And...……. gold jewelry will then be able to be 'seen/detected'...…….. UNLESS/UNTIL "wet-salt" is introduced. Then we're back to square-one. When a VLF must be configured to 'tune-out' the wet-salt...…. it also tunes out most gold jewelry. Yes: "MOST".

((( A gold 'ring' is a continuous closed-loop of continuity …… conductively...….,,,,,,,,...…… which poses a completely different principle for detection; hence, 'why' we can find 'rings' ))).

Even though...… with all of the above stated...…. in the overall big picture of things...………………… there's hardly been any money/time/resources allocated/dedicated into furthering PI technology. And THIS is 'why' we are not further with PI advancements. (Maybe Moreland/Tartar will hit a grand-slam).

I’m 71. I suspect I will have to settle for incremental improvement. Lol

Rick Kempf
Gold Canyon AZ- where there is no gold

Using a PI is in many ways very different from a conventional VLF IB detector. Much less processed audio than current digital VLF’s. Great depth at the beach but so far, no discrimination in the sense we are all used to it. Sure, experienced users claim (probably correctly) that they can avoid digging a lot of ferrous trash by sound, but it’s an acquired talent - paid for with a lot of holes.

Hopefully this thread will begin to concentrate on the completely different strengths and weaknesses of PI’s and how a dedicated hunter can turn them into GOLD.

For example. How can the pulse delay control on a PI help avoiding digging foil and split shot and when is it appropriate to do that - accepting the loss of tiny gold which goes along with it?

Iron - what can be done to minimize digging it with a non-ground balancing PI and what tools does a ground balance control on current or future PI’s present to help with this.

In both cases above, does a PI present an opportunity to “see through” - in the one case small aluminum - and in the other case ferrous trash - and nail a nice gold ring beneath - which would be totally masked to a VLF IB machine - multifrequency or otherwise?

Rick Kempf
Gold Canyon AZ- where there is no gold



Edited 1 time(s). Last edit at 06/22/2018 11:17AM by lytle78.

If my time is limited …. on making a post; I must then learn to present incrementally. Here goes:

To create a very good (read: successful) PI detectorist:
For someone of whom has never used a PI detector...…. it is my strongest recommendation to 'push' you into digging EVERYTHING in the "all-metal" mode …. in a good location(s) in the wet-salt……….. for at least the first 300 hours. The skillset acquired is priceless. Yes, , , I'm aware "time" (and efficiency) is also priceless (limited)..... in concert with age/health/capabilities/limitations. Most PI's present 'raw-audio'. There is a lot of data to be gleaned from exactly this type of audio..... and presents (tuitionally)…… a priceless intel databank unto which a much higher order-of-magnitude (unsuspecting) skillset will be basised off of. If you have ever hunted with a VLF detector in a monotone all-metal (auto-tune) capacity...….. this counts towards the priceless learning experience. You will see small/shallow targets have a very distinct, discrete audio presentation. You will see medium sized targets will present a DIFFERENT (and learnable) discrete audio presentation. You will see large targets also have their own distinct, discrete audio presentation. On a subconscious level...…. you may not know that you are even doing it...…. you will raise the coil over a target.,.,.,.,.,.,.,., and see/feel/witness/gut that the target ramps down in signal-strength/size/breadth/width/girth TOO fast.... for as little as you raised the coil (whilst performing sweeps)……….. and suddenly realize that the target is tiny/surface/shallow. You only raised the coil one inch...…. and the loud target suddenly became extremely weak.
Or...…. you raised the coil several inches...….. and hardly noticed any form of signal-strength degradation; . . . . . . . . . . Hmmmmmm……… a much larger target.
Or...…. you rotate your body 90-Degrees...…. and the target is now presenting a double-beep. Hmmmmmmmm………… bobby pin or nail. (A elongated ferrous target).

Your coil passes over a hole in the wet-salt sand...…. and you hear a large weak target audio response: Yep. Expectations met. Sweeping the coil on the wet-salt...….. then no wet-salt (the hole)……. then wet-salt again.,.,.,.,.,.,., caused a 'target response' because you (properly) have your PI unit running hot....on the edge of instability. The response you got over the hole in the sand is very characteristic/typical of such incursion. Because of 'experience' (read:skillset)……. you continue to progress/move on down the pike. . . . . . . . not wasting time on the 'target response' from the hole in the sand.

You 'bump' your coil on a seashell …. or divot in the wet-sand...…… and your detector 'squawks'. You continue to move-on-down-the-pike...……… because this "detector behavior" is per your expectations …… due to experience/skillset.,.,.,.,.,.,.,.,.,., so you (no longer) waste time investigating the audio 'squawk'. Your experience/skillset is allowing you to get to the targets that count...…. at a MUCH faster (more efficient) rate.
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Of all my experiences with the (rudimentary/crude) forms of Discrimination employed with PI units (((Thus far..... on our PI technological advancement time-continuum))) ...……. I have experienced something disconcerting. When you rotate (change) the Discrimination set-point ……. usually a form of Ground Balance shift...………… certain conductive bandwidth targets NOW become weaker/less detectable. And...…. in furtherance ……. other conductive bandwidth targets become completely undetectable. For instance: Lets say that you rotate Discrim to 'just barely' discriminate out a Zinc Penny. You will then see/experience/notice/learn that conductive targets that are just barely below the conductivity of a Zinc Penny....,,,,, now become hardly detectable. This may be a large gold signet/class ring.
You may also notice that quite a bit of depth and/or sensitivity is lost …. if you invoke the ID/Discrimination mode. Yes, All-Metal mode is usually much deeper...…… and much more sensitive to small/low-conductive targets. Critical tuition & knowledge. Select your 'Mode' accordingly.

I believe it was Jeff Foster who mentioned it in one of his books........ disc/notch out a single digit and it affects at least 3 to 5 digits on either side. I can relate to the learning process of hunting in say PP mode with an Xcal..... after awhile you just know there nothing in that depression or those tones of hitting objects on the bottom..... or even the minerals when you run against the grain. You become a quick study...... and honestly its like picking up any new water machine even a disc one you learn how it reacts and when it reacts differently ..... so do you.

The "hole", and the reason for the existence of the GPZ.

HH
Mike

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 retain good sensitivity to small targets.

There's always the concern that...….. if you are swinging 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 target that presents a short audio response to begin with. , . , . , . , by virtue of swinging the coil too fast; you will merely shorten the length of the audio response of that small target...even further………… whereby YOU (the human) may not detect the targets presence; yet, the detector will still detect it. In this case; the targets audio response may simply sound like a 'click' or 'tick'. . . . . . and you may just think it's static......or a tiny false audio report.


Once iron is 'lit-up'..... it electromagnetically decays at a much slower rate. It'll keep 'transmitting' for a long time. Non-ferrous targets (the ones we choose to find)…… electromagnetically decay at a extremely fast rate..... or..... don't transmit 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 pass your coil over a gold stud earring that is the size of a BB...… you may not hear it at all. If you 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) will be minimal.

Many folks call PI detectors "iron magnets". There's a lot of truth to this...….. as...……. the targets that PI's find the-most/extremely-readily ….. are ferrous targets. . . . . . . and to tremendous depths.
Ferrous targets = Transmitters
Non-ferrous targets = Non-Transmitters

In short order...….. you will develop a keen ear to ferrous targets (vs. non-ferrous targets) with a Pulse Induction unit. There is a very distinct audio signature to differentiate between the two...… that can be learned quickly.

Reducing your Pulse Delay to a faster rate...…… sensitizes the detector to smaller/thinner targets.

If a PI detector allows you to change the Transmit pulse length (say from 60uS to 120uS)…….. this does 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 linear 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 anyone. )))

Hi Tom,
The PI learning curve is more severe and not many VLF Design Engineers are going to put in the time to learn how to use a PI well, yet they will be on the support staff of the PI projects. They will need this information spoon fed to them. And not many folks have the spoon like you and Clive do. So if you don't give the actually user information, they'll not get "it", or the need for "it"

So Yes, more please.

HH
Mike

That short audio response is another reason for good coil control ....... and better headphone response. That batter life reduction....... i assume that has to do with the detectors audio response based on more targets and nothing to do with the coil? Smart bunch of guys we have on here........ so thanks for all this Tom.