Log Plots of Object Signals.

[Anonymous]

JC,
Thankyou. I'm sorry, but I disagree. In 5,506,506 Candy illustrates the ferrous responses decay far slower than non-ferrous. (F1(c) Candy's efforts to deal to ground mineralisation are met [in 5,576,624] by the last samplings - the L and LB periods - which I hav'nt mentioned before.
My belief - as far as 5,576,624 goes, Candy doesn't digitise at all. Granted, in 5550,650,6 Candy does utilise a "look-up" function, but (and I sincerely ask - does he or doesn't he, subsequently?) I believe the SD 2100 to be completely analogue.
Surely JC, long pulses use power.
g.

 

[Anonymous]

Very interesting all the dispute ,if the SD2100 o SD 2200 is all analog o digital,if this patent is that o this ,and I see also many engineers around. Personnaly I do not spend $ 3000 in a SD (It is the cost of a good oscillo),because it is NOT the top level you say,some days ago I have one in my hands and I check it well in my volcanic soil here in Mexico and it is not "the panacea",I compare it with a "old" Goldscan ,and for a few inch gain in THE SOIL I prefer my goldscan, and SD is also bulky,heavy with cables all around....not really for fields research. Guys,I read students here have goods instruments(oscilloscope,etc...),and nobody take "the bull from the horn",take probes and check this FFFFamous SD ...,now with all the equipment you have,TO DAY NO MYSTERY EXIST and all the dispute go to the end,shut down to move to more constructive ideas.I am a small technicien ,and If I have this detector he took me one minute to open and with a fews hours ,perhaps a day I know the technique of Pulse employed.(if it is nottoo microprocessor design because I'm 48 old !...).
It is not Space engineering ,it is JUST another pulse detector.
Please more on dsp technique,and someone have experimented combining pulse with "two boxe" arrangmend..
And guys,please again ,ONE DAY,open a small $400 SONAR / FISHFINDERS and you will see the FUTURE of a metal detector combining Dsp pulse technologie (Sorry for the delay in Marine equipments you have big money envolved ,it is not the case for PI )...
Thank you all the students and particulary the teacher Eric..Alexis

 

[Anonymous]

Hi Alexis,
I don't see any dispute, Alexis, neither do I see where I say the SD are "the top level".
I see a forum of thinking, exploring, creative, learning people who are attempting to advance knowedge of a topic which, understandably because of commercial reasons, is shy of disclosure. I admire the attentions of Eric FOSTER to this site; I am full of admiration and respect for him - because he too cares about knowledge - and - knowing much more than the rest of us - is willing to patiently share.
Candy too, is just a very clever thinker. But he too, like Eric, has been willing to share - via patent papers. Take away the patent disclosures, take away this forum, and what areas do we have left from which to learn?
Ok! You don't like the SD. Perhaps the SD doesn't like Mexico. You like "two-box" O.k, fiddle, understand, learn, and then share with us in the forum. We all learn. Put your probe into the SD, then post here how it works. Put your probe into your Goldscan - and I will read your posting with interest.
The topic really doesn't matter - someone will be interested - or someone may have just the answer that satisfies you. eg. I've been palying with audio indication thresholds - a slow tick background, and a whistle for the target indication. Someone just may be interested.
g

 

[Anonymous]

In patent 5506506 there is a microprocessor (see page 1). He makes three time constant siganls, short, medium, and long. Then take the log of the short/medium and the log of the long/medium. These values are unitless. However on the baseline of figure 3 he also adds some times in microseconds. What do these times really represent? It is these two signals I refer to in the above posts. They then go to a look up table. Oh by the way the microprocessor has an A/D converter in it or hooked to it, donesn't matter for the patent. Look at it again.
He has lots of nice equations and they all may be correct, but I know how the real world is and sure they had to tweak the look up table a bit.
This patent was applied for in Jan 1993. Which detector do you think it represents?
(Answer none)(They all got changed or some of the patent discloses wrong sample times or such, but still good enough to sue with, without giving everything away)(And sue with one patent for a line of detectors).
JC

 

[Anonymous]

Hi JC,
Thankyou. Yes, you're right in that 5,506,506 incorporates a microprocessor, and no, to a subsequent question, I have no idea whether Candy utilised 5,506,506 commercially.
This paper really assisted - insofar as an appreciatrion between ferrous and non-ferrous target responses go - Fig1A and seq.I can see why he was attracted to differing sampling periods - an endeavour to deal to the heavy mineralisation of Australia??
I must confess Fig3 lost me - I have no knowledge of micros. I got as far as determining the solid dots were ferrous, the crosses non-ferrous, and the circles theoretical 1st order responses - the "look-ups" you mention?
Paper 05576624 doesn't mention microprocessors, and because it shows two manually adjusts, I just presumed that this was the SD2100.
Anyone can be wrong - I was for the way I entered this forum. Candy is - try and reconcile the gates in fig4 with his table on page 17.
I don't know how the word "sue" - nor any history behind it, helps us at all.
Yes, I am listening to Eric - I bought some 709s today!! Eric is probablt too modest to mention, but I invite forum members to read his article on pulse-tesdting of loudspeaker cables - Electronics World, Dec'96Pp930-934.
A posting by Eric to this forum has aleerted me to the drain/source capacitance (Crss??) in a mosfetMay I invite you, Eric, to comment how peretinant it is to the coil response. I know it will slow it's decay, but it it worth excluding with a fast diode?
g

 

[Anonymous]

You entered the forum fine. I am some times very sarcastic about things. Fig.3 is basically the big deal about this patent. It shows how the detector is going to ignore this junk (drill bit, paper clip, small nail, another small nail). ferrous objects. Or at least shows a brillant thought on how this could be accomplished. Doesn't mean anyone actually made one, well they did but couldn't say it could ignore this stuff, cause up close it couldn't.
You "sue" someone when you take them to court (law) in an effort to get money compensation. The only reason there are patents. However, judges and lawyers don't understand this stuff either, so can go either way in court. So you have to dress it up with lots of equations and big thoughts, I mean you have seen other patents. This guy must know what he is doing. (Actually it is a good piece of work, and worth study).
His patent for search head is cute too, doesn't mean minelab ever used litz wire (cuts into profit margin) but if you use real fine stuff Candy can get you cause he showed that below a certain size the eddy currents don't flow enough to bother you.
Have Fun
JC

 

[Anonymous]

Reviewed the patent again. He talks about the metal during the transmit phase (power on the coil) as well as when it is off, especially right after it is turned off. But then changes to talking about only sampling after the turn off. Signal during transmit is puny for practical stuff.
He speaks of long time constants of large ferrous objects and the fact that they have at least multiple order decays, where ferrous is first order only. first order being a simple L/R circuit.
Of course large objects, (ferrous or non), produce long decays which can be sampled much later. Small objects, or distant, will have to be sampled very close to the end of the damping decay, or you never have any signal to even play with.
So what you got to do to discriminate is determine the shape of the rate of decay. Attempts at this have been tried before.
This gets messy when you have multiple targets under the coil and toss in some black sand and wet beach.
Honest enough, Candy even says the data is emprical and in a look up table. Hush my mouth. Sure them guys at minelab are sick of swinging targets in front of detectors.
JC

 

[Anonymous]

Hi JC, Graeme and all,
Non-ferrous objects only show a first order response for times later than one time constant. By that time (late time) the amplitude has decayed to 0.37 of the starting value while the noise has stayed the same. Prior to one time constant, the response is a sum of early time (skin effect) and medium time (diffusion) and the underlying first order. This is why the larger non-ferrous objects on my log plots still show a curved response; they haven