field test unit no 001 "model T"

[mickstv]

http://www.geotech1.com/forums/attachment.php?attachmentid=26737&d=1381835423

Connect any of the popular opamps directly to M2 and your switch turns on and stays on resulting in a cooked opamp. Wouldn't it be best to iron out these problems before declaring it a major achievement??

I actually tested that circuit some time back, using a NE5534 then a lower noise OPA1611, connected directly to the output of the M2 fet Both IC's survived the experience.

[robby_h]

1. As you say "PI science is very mature now" .... Eddy currents do exist ... nuff said. John Heenan is entitled to his opinion.
2. I dont measure changes in the spike current or voltage or changes in the coil inductance.
3. New discoveries are not predictable or they would not be discoveries but be called "confirmations" or something similiar.
4. Not sure how you are comparing the spike decay time or shape to VLF .... but as I said I dont measure the spike decay time or shape.
5. Golly .... thats a leap ... because you say "PI science is very mature now" .. therefore you have proved nothing new can be discovered about it. ???
6. People are not using my method .... because obviously it has not been invented till now ... so I dont have to ask them.

As I said, I think it best to ask why others aren't using a particular method instead of assuming you have discovered something new.

I suppose it all depends on what you call a discovery. It could be something you didn't know but is well known to others.

Re Post 866 of this thread, you posted something very similar in 2009 here http://www.findmall.com/read.php?34,920760,page=1

That was almost 5 years ago and in recent posts on an Oz forum you say "it may have shortcomings" and needs "a lot of field testing". It would make more sense if you prove the concept before declaring it a major advance in detector design.

http://www.geotech1.com/forums/showthread.php?17287-field-test-unit-no-001-quot-model-T-quot&p=157025#post157025

Your pictures (post #340) show a grossly under damped waveform and picture three shows what we would expect to see when a non-ferrous target is presented to an under damped coil. The apparent phase shift though shown and highlighted in picture four is an illusion caused by an incorrect trigger, ie, you triggered off the trailing edge instead of the leading edge.

With this mistake corrected, it should then be obvious that the spike decays faster for non-ferrous objects and decays slower for ferrous objects, exactly as we would expect. The problem though is that highly susceptible material such as magnetite has the same affect as a ferrous object and will completely overwhelm any small change caused by a target at depth and you can't apply traditional GB to your waveform because it is heavily contaminated with the x component that we deliberately avoid in traditional designs.

And your definition of "damped" is different to the industry's definition. If Eric Foster said he had the spike damped in 8 usecs then most people here would assume he meant the spike had decayed to 0 volts in 8 usecs. You say you can sample at 1.8 usecs in one instance and at 4 usecs in another but the waveform is still settling somewhere off the page. This would be a disaster if we attempted to apply traditional sampling at the times you mention.

In Post 866 of this thread you mention period C, supposedly decaying for some 100s of microseconds but this decay doesn't exist in traditional PI where the the spike has ideally settled to effectively 0 volts before sampling begins.

Your automatic self switching rx switch also seems to be a bit iffy. http://www.geotech1.com/forums/showt...130#post179130
Picture at

http://www.geotech1.com/forums/attachment.php?attachmentid=26737&d=1381835423

You said elsewhere that this switch makes 6 patents that use front end switches obsolete but how is this possible when it must be followed by a conventional switch in order to work??? Connect any of the popular opamps directly to M2 and your switch turns on and stays on resulting in a cooked opamp. Wouldn't it be best to iron out these problems before declaring it a major achievement??

[Carl-NC]

And Doug is trying to get blokes to invest in your detector.

Actually, Mr. X is someone else.

[PATCHES JUNIOR]

NO ONE has asked for any money in relation to this detector .. and the post says nothing about ground balance ... nothing about gold detection ... nothing about minelab and the 1000 gain you are talking about is completely out of context ... SO CHECK YOUR FACTS OR YOUR EYEGLASSES.

I never said "you" said this. If you read it again, I said Doug said this. So I guess we both need new glasses. And as far as Minelab, Doug never said Minelab directly. But who else would Doug try to discredit Moodz? And Doug is trying to get blokes to invest in your detector. And he DID SAY it would be a 1000 times better than the current offerings available. And you say no ground balance circuit in your detector. Read your post!!!!

[Paul99]

Looks like John had to duke it out with conventional PI proponents ...

http://en.wikipedia.org/wiki/John_C._Heenan

I thought John was the Archbishop of Westminster, and was relying on Divine Intervention to get his metal detector working.

http://en.wikipedia.org/wiki/John_Heenan_(bishop)

John did have high hopes for his detector. Here is a link to archived data from his web site....

http://web.archive.org/web/20130718212720/http://zgus.com/

[Silver Dollar]

Looks like John had to duke it out with conventional PI proponents ...

http://en.wikipedia.org/wiki/John_C._Heenan

[moodz]

John Heenan argued that eddy currents don't exist and said a pi detector instead measures changes to the coil's properties caused by a metal object. This obviously includes changes to the coil current. He also argued that pulsing a coil to generate a high voltage pulse just to measure the changes in the spike is a waste of time because we get the same result during the pulse on-time, therefore we could measure changes to the coil's properties when just transmitting a continuous low current square wave. He did both.

The old PI classroom has numerous posts from novices who noticed how a metal object alters the coil's properties, ie, the spike's shape, tx shape, coil current and inductance, and some actually thought they had discovered something new when in fact it is something any engineer would predict without ever building a circuit. We can't call this a discovery because it is predictable.

Although some text says otherwise, traditional pulse induction does not measure the affect the target has on the spike's decay time or shape. If it did then PI would have no advantage over VLF and it would also have more problems to solve than VLF.

PI science is very mature now. I think it best to ask why others aren't using a particular method instead of naively assuming you have discovered something new.

1. As you say "PI science is very mature now" .... Eddy currents do exist ... nuff said. John Heenan is entitled to his opinion.
2. I dont measure changes in the spike current or voltage or changes in the coil inductance.
3. New discoveries are not predictable or they would not be discoveries but be called "confirmations" or something similiar.
4. Not sure how you are comparing the spike decay time or shape to VLF .... but as I said I dont measure the spike decay time or shape.
5. Golly .... thats a leap ... because you say "PI science is very mature now" .. therefore you have proved nothing new can be discovered about it. ???
6. People are not using my method .... because obviously it has not been invented till now ... so I dont have to ask them.

[Carl-NC]

PI science is very mature now.

I would completely disagree with this.

[robby_h]

John Heenan argued that eddy currents don't exist and said a pi detector instead measures changes to the coil's properties caused by a metal object. This obviously includes changes to the coil current. He also argued that pulsing a coil to generate a high voltage pulse just to measure the changes in the spike is a waste of time because we get the same result during the pulse on-time, therefore we could measure changes to the coil's properties when just transmitting a continuous low current square wave. He did both.

The old PI classroom has numerous posts from novices who noticed how a metal object alters the coil's properties, ie, the spike's shape, tx shape, coil current and inductance, and some actually thought they had discovered something new when in fact it is something any engineer would predict without ever building a circuit. We can't call this a discovery because it is predictable.

Although some text says otherwise, traditional pulse induction does not measure the affect the target has on the spike's decay time or shape. If it did then PI would have no advantage over VLF and it would also have more problems to solve than VLF.

PI science is very mature now. I think it best to ask why others aren't using a particular method instead of naively assuming you have discovered something new.

[moodz]

Agreed, he didn't acknowledge eddy currents.



He was examining and measuring the transmit and spike/flyback currents. The transmit is basically the same as flyback during abrupt transitions.

Thats like saying lets use antigravity to power spaceships .... does that mean I have now invented antigravity ? Are you able to quote a post or more substantial information ( eg patent ) where a method of doing this is described ?

[Paul99]

Mr. Heenan adamantly denied the existence of eddy currents.

Agreed, he didn't acknowledge eddy currents.

I read his posts for a while for the entertainment value, but I don't recall he proposed anything like this.

He was examining and measuring the transmit and spike/flyback currents. The transmit is basically the same as flyback during abrupt transitions.

[Carl-NC]

Mr. Heenan adamantly denied the existence of eddy currents. I read his posts for a while for the entertainment value, but I don't recall he proposed anything like this.

[Paul99]

Unless you can point to patents or other definitive prior art ... your post is off topic also.

I don't need to point to anything. John Heenan proposed the same concepts as yourself many years ago. Why don't you look him up and learn something for a change.

When it came to the crunch it didn't work for John Heenan either.

[moodz]

Moodz, according to my detector design guru, this idea you have is as old as Methuselah.... or should that be Adam???

EDIT:.... do you remember our mate John Heenen??

Unless you can point to patents or other definitive prior art ... your post is off topic also.

[Paul99]

NO ONE has asked for any money in relation to this detector .. and the post says nothing about ground balance ... nothing about gold detection ... nothing about minelab and the 1000 gain you are talking about is completely out of context ... SO CHECK YOUR FACTS OR YOUR EYEGLASSES.

_____________________________________
( copy of my original post below )
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It seems that some are unware of patented active damping techniques or maybe cant read or need a simple explanation.

HOW CURRENT PI detetectors work. ( simplified )
The pulse induction detector as known in the art ( ie the ones you can buy today ) generally has three states.

A. A transmit period during which a current pulse is passed through a coil. eg 200 microseconds

B. A flyback period during which a high voltage back EMF develops across the coil and the peak current in the coil rapidly decreases. eg 5 microseconds.

C. A decay period during which the residual current/voltage from the flyback period decays exponentially. A damping resistor is usually connected across the coil so that the coil does not ring during the decay period. eg up to 100s of microseconds.

The increase and decrease of current in the coil ( di / dt ) during period A and B cause eddy currents to be generated in conductive targets. These eddy currents in most targets will persist beyond period A and B above and can be detected by sampling the decay voltage or current of the coil in period C.
As you swing across a target the decay curve in C will change slightly and this is sampled and amplified and makes a beep or whatever in your headphones. Of course in a well designed detector there will be more carefully timed samples and processing to eliminate ground and the earths magnetic field both of which will appear as false target indications if you dont compensate for them. There are lots of patents and designs focusing on how to sample and pulse timings to improve these areas.

However dear reader there are very few patents on damping ... ( much to my relief ) ... because everyone has assumed that a damping resistor is the optimal way to damp a coil. Damping mathematically or practically applies to a system where you wish to modify an oscillating system. Oscillators are narrowband systems ... when in fact the PI is a broadband pulse system and when we talk about pulse systems we are talking about equalisation and impedance matching ... not oscillators.

Anyway I digress ... back to why the moodz detector is better..... there are a number of reasons but one of them is this.

Lets assume energy stored in the magnetic field during period A ( the tx period ) = 1.0 joule.
During period B ( the flyback ) most of this energy returns to the coil as the magnetic field collapses. Lets say 0.9 joule.
So where has the 0.1 joule gone ? Some is lost or stored in the ground, some is radiated as EMI and some is "stored" in the target as eddy currents.
The decaying eddy currents in the target are detected during period C by your standard PI detector. ( remember the decay curve ).

HOWEVER ... there is a complicating factor .... if a target is a distance X from the coil the eddy currents stimulated in the target during period A and B will be reduced by a factor of 1/XxXxX or one over X cubed. Call this the transmit path loss. During period C the same rule applies there will be a further path loss of 1/XxXxX as the standard PI detector tries to detect a target eddy current during period C. In other words the TX loss multiplied by the RX loss is 1/XxXxXxXxXxX or one over X to sixth power. All of this because the standard detector measures the target "return" signal during period C. This maths has been simplified the real maths still demonstrates the advantage.

The moodz detector does not measure the target return during period C ... there is very little decay curve to sample in period C because the active damping control loop of the moodz detector minimises this "error" voltage. The moodz detector effectively estimates the energy stored in the target ( ie the eddy current ) during transmit by subtracting the energy returned during flyback ( period B ) from the energy transmitted ( period A ) ie instead of measuring C we measure B - A This is just like alegbra :-) ..... except here is the killer ...... by measuring B - A instead of C the path loss to the target is only 1 / XxXxX for the moodz detector instead of 1 / XxXxXxXxXxX for your standard PI detectors. Thusly the moodz detector is 3 orders of magnitude more sensitive than your BrandX detector.

In numbers ... simplified and no ground / circuit or radiation losses .... and target is a distance of 10 units from the coil.

BrandX Detector

Period A : TX Energy = 1.0
Period B : Eddy Current Energy in target = 1/(10 x 10 x 10) = .001
Period C : Target decay RX = .001/(10 x 10 x 10) = .000001

ie RX signal = .000001

Moodz detector

Period A : TX Energy = 1.0
Period B : Return Energy during flyback = 0.999

ie RX signal = A - B = .001

moodz detector is 1000 times more sensitive.

OBVIOUSLY ... because the moodz detector does not try to detect target energy per se during period C ... it dispenses with all that crazy patented sampling schemes used over the years. Target holes ... what are they ? LOL.

There are at least 3 more innovative benefits of the moodz detector arguably as good as the target gain feature which I wont go into here however if you cannot see the benefit of having a 60 dbv increase in target sensitivity then just go and buy the BrandX detectors ... you dont need a moodz detector ... you cant buy one at the moment anyway. :-)

moodz

...he he ... some of this text sounds like it came from a patent

Moodz, according to my detector design guru, this idea you have is as old as Methuselah.... or should that be Adam???

EDIT:.... do you remember our mate John Heenen??