Standardized Tests for Metal Detectors

[Qiaozhi]

A hypodermic needle could not be detected by a PI even when Eric Foster tried it with a 1us sample delay. The shape of the needle, with its tiny cross-section, is unable to sustain eddy currents for long enough to be detectable. I would suggest that the only hope of detecting these items is with a VLF running at a relatively high frequency. In ITMD we discussed the best transmit frequency to use (pages 64 and 65) and it was found in tests that 70kHz was the most the sensitive to small targets. (The tests were done at 3kHz, 10kHz, 20kHz and 70kHz.)

It would also seem a good idea to use a small coil.

[Nupi]

If you are not ready to prove your exaggerated claims, then don't make it.

Are you ready to send me sample of hypodermic needle you use in test?

I'm not saying that I'm not ready to prove my "exaggerated claims". I'm definitely ready to prove it.
I say, "If I show it, then what?" and it turns out to be so than wat?
Will I be ignored or can we debate about? Because it sometimes seems that if there are no points more to score they run heart away!
I am willing to making a video but not to increase our ego but to help each other.

[geoscash1]

I'm not saying that I'm not ready to prove my "exaggerated claims". I'm definitely ready to prove it.
I say, "If I show it, then what?" and it turns out to be so than wat?
Will I be ignored or can we debate about? Because it sometimes seems that if there are no points more to score they run heart away!
I am willing to making a video but not to increase our ego but to help each other.

My momma always said, "The Proofs in the Puddin".... best way to get a point across is to show it being done, to do it, have record of it with witness's, video is the best way to put it to sleep
as long as the item being used is verifiable on video....

For test items I believe that aluminum soda can (small piece 1/2x/1/2 etc.) is the most readily available item in every country in the world along with steel bottle caps and as Davor mentioned, lead fishing sinkers are also an excellent choice which are also available world wide and can be had in as small as 1/10 ounce which can be cut into smaller pieces if needed. Just my thoughts on the subject..

[Nupi]

For test items I believe that aluminum soda can (small piece 1/2x/1/2 etc.) is the most readily available item in every country in the world along with steel bottle caps and as Davor mentioned, lead fishing sinkers are also an excellent choice which are also available world wide and can be had in as small as 1/10 ounce which can be cut into smaller pieces if needed. Just my thoughts on the subject..

Not every alumimium canned soda is from 'aluminum'. There are many soda and beer cans where the thin sides is made of iron.
Also, not all cans are of the same thickness. So simple is not put the world one another.

[Silver Dollar]

Well I believe the fishing sinkers in the US are not allowed to be made out of lead so most are some
kind of steel now..

[Nupi]

A hypodermic needle could not be detected by a PI even when Eric Foster tried it with a 1us sample delay. The shape of the needle, with its tiny cross-section, is unable to sustain eddy currents for long enough to be detectable. I would suggest that the only hope of detecting these items is with a VLF running at a relatively high frequency. In ITMD we discussed the best transmit frequency to use (pages 64 and 65) and it was found in tests that 70kHz was the most the sensitive to small targets. (The tests were done at 3kHz, 10kHz, 20kHz and 70kHz.)

It would also seem a good idea to use a small coil.

Can you tell me how much better? 2-10-30% or more?
The word better is very relative.

[golfnut]

fair point, same as uk.

I got mine as they were catapult ammunition from the bay

[baum7154]

Well I believe the fishing sinkers in the US are not allowed to be made out of lead so most are some
kind of steel now..

---------------------------------------
I think you might be confusing fishing split shot with waterfowl shotgun shells in which lead shot is now banned. CABELA'S sells almost exclusively lead sinkers and split shot in every state in the union with the exception of lead sinkers less than 1/2 oz in the state of New York as follows:

Reusable Split Shot 420-Piece Assortment

Size: Weight (gr.): Weight (oz.): BB 7.4 .017 3/0 9.2 .021 7 16.6 .038 5 32.4 .074 4 42.9 .098 1 70.9 .162

The following note(s) apply to the specific item(s) listed below:New York has banned the sale of lead sinkers weighing a
half-ounce or less. Cabela's is unable to sell and or ship
to the state of New York.

On the topic of aluminum cans I believe that the industry standard worldwide is for aluminum can walls to be .0035" to .004" thick. Thinner walls than this makes the cans too delicate for normal use. All I have measured are in this range.

TO NUPI: If you have the tools please measure some and let us know for sure. In the event that there is a thinner one found I believe that others with a wall thickness of .004" will also be found. Once this is clarified it should be a simple matter of posting what brand of cans will meet the criteria.

Regards,

Dan

[Qiaozhi]

Can you tell me how much better? 2-10-30% or more?
The word better is very relative.

The test was performed a few years ago and I don't have anything but subjective results. It was mainly the relative sensitivity of different targets to different frequencies that was important.

[geoscash1]

You can buy lead shot, split shot or any style of it all day long in just about any place that sells fishing supplies, and it is lead, not steel.... Yes, they are slowly switching to a new "lead free" type of stuff, but it will take 30 years to get rid of the supplies that are still on the shelves in the US..It will always be available from china...
http://www.ebay.com/sch/i.html?_odkw...shot+&_sacat=0

[golfnut]

I got these

http://www.ebay.co.uk/itm/Catapult-S...item3ce278c721

[Davor]

We can always revert to a solder blob. Because of its standardised composition and melting temperature it might be the most consistent and widest available target material in the world. And it reacts similar to bronze coins.

[Nupi]

We can always revert to a solder blob. Because of its standardised composition and melting temperature it might be the most consistent and widest available target material in the world. And it reacts similar to bronze coins.

I agree with that.

[Nupi]

TO NUPI: If you have the tools please measure some and let us know for sure. In the event that there is a thinner one found I believe that others with a wall thickness of .004" will also be found. Once this is clarified it should be a simple matter of posting what brand of cans will meet the criteria.

Regards,

Dan

I do not have a micrometer.

Can Composition
Most metal beverage cans manufactured in the United States are made of aluminium,[4] whereas in some parts of Europe and Asia approximately 55 percent are made of steel and 45 percent are aluminium alloy. Steel cans often have a top made of aluminium. The aluminium used in United States and Canada are alloys containing 92.5% to 97% aluminium, <5.5% magnesium, <1.6% manganese, <0.15% chromium and some trace amounts of iron, silicon and copper according to MSDS from aluminium producer Alcoa.[5] Alloys used include 3004, 3105, or other 3xxx/5xxx series aluminum.[6]
An empty aluminium can weighs approximately half an ounce (15 g). There are roughly 30 empty aluminium cans to a pound or 70 to a kilogram.
In many parts of the world a deposit can be recovered by turning in empty plastic, glass, and aluminium containers. Scrap metal dealers often purchase aluminium cans in bulk, even when deposits are not offered. Aluminium is one of the most cost-effective materials to recycle. When recycled without other metals being mixed in, the can–lid combination is perfect for producing new stock for the main part of the can—the loss of magnesium during melting is made up for by the high magnesium content of the lid. Also, reducing ores such as bauxite into aluminium requires large amounts of electricity, making recycling cheaper than producing new metal.
Aluminium cans are coated internally to protect the aluminium from oxidizing. Despite this coating, trace amounts of aluminium can be degraded into the liquid, the amount depending on factors such as storage temperature and liquid composition.[7][8] Chemical compounds used in the internal coating of the can include types of epoxy resin.[9]
http://en.wikipedia.org/wiki/Beverage_can

Beverage cans today are among the lightest beverage packages, while at the same time being extremely robust and protective of their contents. Today, cans can be produced with a wall thickness of 0.097 mm – as thin as a human hair
http://packaging.world-aluminium.org...ghtweight.html

[baum7154]

http://packaging.world-aluminium.org/benefits/lightweight.html[/URL]

--------.097 mm is equal to 0.003818" precisely in the range of .0035 to .004 I have measured on cans in the USA so they should work just fine as target material.

thanks,

Dan