For nearby wires, e. Material effect on skin depth[ edit ] In a good conductor, skin depth is proportional to square root of the resistivity. This means that better conductors have a reduced skin depth.
Chris's Metal Detecting Page: The Halo Effect njminerals. All articles and images are subject to copyright. They may not be copied or distributed in any way without prior written permission.
I've updated this article to organize it better, and also to add some ideas that further reinforce my primary thesis: There is some fairly advanced science involved including biogeochemistrybut my aim is to distill this into material that a layperson can understand.
The Trouble With Test Gardens T he fresh-burial test for coins has led many a detector owner to conclude his new machine is "no good".
That's because this test is nothing more than a worsened version of the Air Test. You bury a coin six inches deep Perhaps you get no signal whatsoever.
Maybe you even start to become discouraged, thinking you bought a lemon. This is like doing an air test, where the air is made of soil. It fails to take into account an extremely important factor, which we'll discuss shortly. The Controversy The "halo effect" theory holds that buried metal objects have an ionization "halo" that increases their apparent size to a metal detector searchcoil.
This makes the objects detectable at greater depth. In other words, according to this theory, long-buried metal objects have something you cannot duplicate with a recently-created test garden. Many people understand that iron objects form a halo, but they go so far as to claim that copper, silver, and gold cannot form halos.
This is where most of the controversy lies. Their reasoning is that copper, silver, and especially gold are too "inert" to react in just a few years of soil contact. A popular sub-argument is that these metals cannot be forming halos in the soil, because they're not pitted or corroded enough when dug up.
This specious argument is especially common when talking about silver coins.
The skepticism is understandable, of course, since silver and copper have traditionally been thought of as "noble" metals. They're just not as noble as platinum, palladium, or gold. In chemistry, the term "noble" is generally synonymous with "low reactivity". The term is used in conjunction with metals, and gases.
Xenon is a noble gas, for example, while palladium is a noble metal though it's not one of the three traditional ones of antiquity. We're going to see why the halo theory holds true for copper and silver. There may even be a halo effect for gold objects, and we'll see why that is, too.
Does silver ionize in the ground? Pine needles and oak leaves covered the forest floor. It's pretty clear there was sulfur at work here, too.
Silver will give an "ion halo" wherever groundwater or moisture can work on it for decades, especially if that water is even slightly acidic which it nearly always is. When the black coating was removed electrolytically, it revealed only minor pitting of the surface. The volume of sulfide corrosion was relatively large, compared to the apparent loss of metal.
This is an area that many seem not to understand very well.
Corrosion compounds can occupy a great deal of volume compared to the original metals. Let's Think About This H ave you ever dug up an old copper coin and found that it was green with corrosion?
What do you think that means? How about a year-old silver coin that emerged from the soil all blackened with tarnish? Instead, perhaps, it emerged with just little traces of black, brown, or even other colors.Link to Gootee Homepages: The Complete Index.
i.e. Links to ALL of my webpages. My page about Spice Modeling and Simulation of Circuits and Components My LTSpice Stuff: Power Transformer Modeling, DC Servo for Audio Amplifier, and more.
The formation of a trivalent conversion coating on aluminium has been investigated using analytical electron microscopy, atomic force microscopy, ion beam analysis, glow discharge optical emission spectroscopy, Raman spectroscopy and X-ray photoelectron spectroscopy. 5) Commercial proposal ¾ SEHMS General technical description Summary description of SEHMS Pipeline electrical heating system in which unique technique is realized using skin-effect physical.
With over terms defined and explained, Semiconductor Glossary is the most complete reference in the field of semiconductors on the market today. ASTM's paint and related coating standards are instrumental in specifying and evaluating the physical and chemical properties of various paints and coatings that are applied to certain bulk materials to improve their surface properties.
topic Why must Copper Bus Bar be Tin Plated? A discussion started in but continuing through () Q.
Sir, Why do we need Tin Plated Copper bar .