Future technology ?

An interesting read....

[www.sciencewa.net.au]

Tony

This language doesn't quite match up with my understanding of how my metal detectors work -- the "sending back a response" part:


“What [electromagnetic sensors] do is they send an electromagnetic field – you can think of it as waves going into the ground – and then sometimes they hit treasure, a deposit of metal or even water,” Mr Torres says.

“If this treasure, if this chunk of metal or water gets a wave then it reacts to this wave and it sends a response back up.”

The response picked up by the sensor alerts scientists to a conducting object below the ground, which can then be identified using geological knowledge of the area and other clues.

"The response picked up by the sensor alerts scientists to a conducting object below the ground, which can then be identified using geological knowledge of the area and other clues."

so, in the future we will still be guessing!! cant wait!!!!

chuck.

Well, "sending back a response" part is probably a description of the induced secondary field formed on the target. The magnetic field from the primary transmit coil collapses rapidly, which creates the voltage across the target surface, which drives the current (free electrons) which induces the secondary field, which unbalances the balanced coil arrangement between the transmit and receive coil back at the detector, which generates a coil voltage - which makes a beep. You may get a conducting object - non-ferrous, but you also get ferrous through a different route. Ferrous aligns a portion of it's magnetic domains in accord with the field lines from the primary field. When the coil polarity switches (it's an alternating current) the target magnetic field dies, the domains collapse and realign, which generates a secondary field - and you know the rest of the story, it's upsets the coil arrangement. So, the problem is two-fold: separating ferrous from non-ferrous, which is problematic since ferrous has the ability to also generate eddy currents and mimic non-ferrous AND non-ferrous comes in many different flavors - how to differentiate between pull-tabs and nickels, as the phase angles (between the transmit wave and the received wave) are identical.

In the end, a new technology needs to be developed or improved upon, as the current IB design curve has flat-lined at the law of diminishing returns. The smart guys on GeoTech and the design engineers at the big detecting companies will eventually have to go beyond rearranging knobs and buttons and adding clocks and GPS ... someone has to figure out the next big breakthrough. So far ziltch.

Johnnyanglo

I just read the article.

“But if you connect the sensing element of your metal detector to my amplifier … then the small signal coming from the ring is amplified and is big enough that your sensing element can pick it up.”


So the guy is a physicist "UWA physicist Francis Torres" so I can assume he has some basic idea about how metal detectors work. He is not specific about what type of detector he is referencing though. Is it VLF TR/IB or PI.

We know VLF TR/IB is severely hindered by ground minerals and that increased power or amplification doesn't really benefit TR/IB. We have seen attempts though. Remember the various attempts to insert probes in the ground and charge the ground prior to detection in the attempt to amplify responses?

But again, here we tend to think in terms of coin size targets. Two box units can be measured in meters based upon target size.

We know PI is not as severely hindered by ground minerals and that increased power or amplification can be a benefit. PI also does not need to rely on "rate of change" to pull a signal out of minerals. It may be that some type of amplification would be beneficial to PI depth.

Anyone ever made a two box PI detector?

:shrug:

By the way, they already see deep into the earth with some detail using sound waves. I don't see an acceptable way to use acoustics in hobby detectors.

:shrug:

HH
Mike

If you dig far enough back in the technology forum on Find mall you will find discussions about two box PI detectors generally speaking as I recall they were not worth the trouble.

Rick Kempf
Gold Canyon AZ- where there is no gold



Edited 1 time(s). Last edit at 06/13/2014 07:36PM by lytle78.

Call me a cynic, but when I read things like:

"Mr Torres, who worked on the project as part of his PhD research, says the amplifier is built on an interaction between light and sound and is probably 10-20 years away from being ready to use."

...about 10 flashing red lights go off in my brain. They might have well have said, "It's sort of an amplifier involving something called 'physics', but it's decades away from actually working."

Admittedly, the article was probably written by a (very) non-technical person from notes taken during an interview with the gentleman, so he's probably not getting a fair representation.
And if he's got a real breakthrough, he won't want anyone stealing his ideas...so a certain amount of imprecision is expected and warranted.

And of course, if it really works to give us extra depth in the real world, I'll be first in line to buy it.

mike

After some more research,
Here's a link to a more technical description of what it does...looks like it amplifies subtle mechanical vibrations. Not sure how that could help metal detecting, but he's enjoying to listen to. And you've got to give a break to anyone who wears a red bow-tie.
[freshscience.org.au]



Edited 1 time(s). Last edit at 06/13/2014 09:08PM by Mike in CO.