Standardized Tests for Metal Detectors

[Davor]

I think a completely standardised soil and target conditions are necessary for avoiding apples vs. pears competitions in the future.

[baum7154]

Do you mean competitions in one location or worldwide with results sent in for inclusion in a database? In one location all are competing on the same soil. It seems to me that standardized soil conditions in nature will be very difficult to find. Can we easily create a standardized soil? I'd be all for that, but how? The standardized targets by comparison are easily achieved.

Dan

[geoscash1]

I think standardized soil would be a very difficult feat to accomplish for a world wide test... In my area of the country (Nor CaL) I can move six feet and the soil/ground is very different.

Thinking about it, something everyone has access to, aren't batteries a common item world wide, why not a button style (watch battery) for small item common test target.. batteries make a decent target for testing and they should be accessible everywhere and are very cheap on ebay. They are made to a specific tolerance and of the same material and size so should be an easily attained item for everyone... Just thinking out loud...

[Davor]

And perhaps in a good direction. I'm not sure if, say CR2032, have steel bodies, and if it is not steel we have a perfect target.

I guess a perfect standard soil equivalent could be plain tap water. Conductivity can be adjusted by adding salinity.

[Qiaozhi]

Personally I'm not so interested in producing a chart indicating how various commercial detectors react to our standardized tests. I think it's up to the individual to carry out their own tests and see the results first hand. Any chart we create will be hotly contested anyway by the those that find their favourite detector didn't quite cut the mustard, and that's not really the purpose of the exercise. However, I do think a comparison chart would be most useful for some of the projects presented here on Geotech. It might also give some direction for future development of these projects, as we work to develop methods of passing the various tests. Some of the tests will only be relevant for PIs, whereas others will be more appropriate for VLFs.

As far as soil tests are concerned, I suggest we have a maximum of three for inland soils: light (1), medium (2) and high mineralization(3). Previously I suggested a panel covered in iron ferrite cores for test 3.

Has anyone tried the "wood, coin (nickel) and iron nail test"? ->
https://www.youtube.com/watch?v=qWen...ature=youtu.be
I tried this yesterday ... and the results were very interesting.

[Nupi]

Has anyone tried the "wood, coin (nickel) and iron nail test"? ->
https://www.youtube.com/watch?v=qWen...ature=youtu.be
I tried this yesterday ... and the results were very interesting.

Yes, I have tested it.
What are the sizes, depth and distances between nails and coin that you tested?

[geoscash1]

Psds on CR2031 silver oxide button battery

Davor, it looks like the 2032 and other batteries casing is steel based on what I'm seeing in the psds and cr2032 data sheet, I thought they were stainless....
silveroxidezinc_psds.pdf
cr2032.pdf

[Davor]

So unfortunately these batteries are useless. Stainless steel is a difficult material to detect. Maybe some other type of batteries will do.

[green]

Been trying to understand what it takes to detect hypo needles. Stainless has a conductivity about 1/10 of nickel. Solder was mentioned as a possible test target. Conductivity between stainless and nickel. I plotted some targets made with solder, a nickel and a silk pin. Couldn't see a 39 mm piece of solder until I wrapped the solder in a circle. Wondering if amplitude or a short time constant is the reason. Is a VLF detector better for detecting straight low conductive targets?

[Qiaozhi]

Yes, I have tested it.
What are the sizes, depth and distances between nails and coin that you tested?

Same as the video.
Obviously it's difficult to find the same size and shape nails, and in fact the ones I used were slightly larger, which should make detection of the coin more difficult. The coin was a U.S nickel (5 cents), but I also tried the same test with a Euro. Distance between the nails was 4", with the coin in the middle. Depths were 2" and 4".

[Nupi]

Same as the video.
Obviously it's difficult to find the same size and shape nails, and in fact the ones I used were slightly larger, which should make detection of the coin more difficult. The coin was a U.S nickel (5 cents), but I also tried the same test with a Euro. Distance between the nails was 4", with the coin in the middle. Depths were 2" and 4".

That is a very good result, I think you've defeated the Deus!

[baum7154]

Been trying to understand what it takes to detect hypo needles. Stainless has a conductivity about 1/10 of nickel. Solder was mentioned as a possible test target. Conductivity between stainless and nickel. I plotted some targets made with solder, a nickel and a silk pin. Couldn't see a 39 mm piece of solder until I wrapped the solder in a circle. Wondering if amplitude or a short time constant is the reason. Is a VLF detector better for detecting straight low conductive targets?

What diameter of solder did you test?

Dan

[green]

(What diameter of solder did you test?)

.8 mm. Was hoping someone could test a piece 39 mm long. Info is on the graph reply #129. I'm thinking it has a very short time constant but really don't know. All I know is I can't see it with my test setup. Maybe if I could sample at less than 3 usec. Graph is a plot of change in amplifier out.

[baum7154]

Thanks I should have looked closer at the attachments before asking. I could not detect the 39mm solder sample with any reliability, could get intermittent detection but it was not what I call reliably correlated to the target passing the coil.

Dan

[baum7154]

In the test above the solder sample was simply a 39mm straight piece of the 8mm solder, resin core. Did not form it into a loop. I wonder if it would be detectable if it was pounded into a 6mm wide strip?

Dan