Designing and marketing new metal detectors.

[sawmill]

WM6

Are you talking about a Garret Pro pointer?

[ivconic]

Needle i tested is "made in Switzerland", top quality.
Just measured it; metal body is 24mm long and 0.3mm diamm.
Not magnetic at all, also checked it with small neodymium magnet.
So... no wonder why Deus remained "calm" on it.
Maybe i should search for other type of needle?
Whatever, that is not the point here.
Small titanium screw WM6 sent me is quite proper "target" for testing detectors.
As i understood him; such screw is standard type and can be obtained anywhere.
Cheers!

P.S.
In next few hours i am expecting friend with White's Spectrum. So i will test it and Troy X5 on screw and needle.

[WM6]

WM6

Are you talking about a Garret Pro pointer?

Yes, Garrett.

[sawmill]

WM6
That explains a lot. The Pro pointer is only a 12 KHz detector,
and not capable of hearing real small objects. The GM3 is a real
detector designed to find very small objects in mineralised soil.
It is a 50KHz machine that can be adjusted for the job at hand.

You can not compare a pin pointer,or a coin relic machine to a
VLF that is designed to find tiny gold ,at higher frequencies for
grain size objects. The Gold Bug 2 even runs at a higher frequency.
This is why I recommend these two machines for serious prospecting,
as in locating tiny gold in a quartz stringer,or the invisible gold that
Reg speaks about.

[WM6]

Sawmill, here I am talking about stainless hypodermic needle detecting and not about tiny gold detecting.

I tested those needle by two detectors designed for tiny gold detecting, with Garrett AT Gold Pro and Tesoro Daiblo II (bot with stock elliptic coil). Both of those detectors can detect gold nugget of about 1gram at about 12cm (5") with easy. But no one can detect those needle even in close touch. No voice at all. Nothing. And propointer can detect every metallic dust in soil, but not those needles.

As ivconic report the same with Deus at 18kHz frequency.

Regarding frequencies. Look carefully at ivconic test of small titanium bolt here:

http://www.geotech1.com/forums/showp...1&postcount=92

As you can see, there was 1.1 gram titanium bolt tested on "Wet Beach" program too, this was at 18kHz, but barely 1cm of "depth" on other side in Relic program, working at 8kHz, this small part can be detected at 14cm. So, there is not all secret in frequencies used.

Maybe with smaller coil will go, I dont know, I have no one at this moment to test it. Fisher GB2 is coming out mostly with smaller coil, maybe it can, but I need real test report (excluding errors as hand detecting) and not presumption only.

[Tinkerer]

Sawmill, here I am talking about stainless hypodermic needle detecting and not about tiny gold detecting.

I tested those needle by two detectors designed for tiny gold detecting, with Garrett AT Gold Pro and Tesoro Daiblo II (bot with stock elliptic coil). Both of those detectors can detect gold nugget of about 1gram at about 12cm (5") with easy. But no one can detect those needle even in close touch. No voice at all. Nothing. And propointer can detect every metallic dust in soil, but not those needles.

As ivconic report the same with Deus at 18kHz frequency.

Regarding frequencies. Look carefully at ivconic test of small titanium bolt here:

http://www.geotech1.com/forums/showp...1&postcount=92

As you can see, there was 1.1 gram titanium bolt tested on "Wet Beach" program too, this was at 18kHz, but barely 1cm of "depth" on other side in Relic program, working at 8kHz, this small part can be detected at 14cm. So, there is not all secret in frequencies used.

Maybe with smaller coil will go, I dont know, I have no one at this moment to test it. Fisher GB2 is coming out mostly with smaller coil, maybe it can, but I need real test report (excluding errors as hand detecting) and not presumption only.

Well, this thread has taken an unexpected turn, but it is still within the scope of the title.

A detector designed to detect discarded hypodermic needles.

Can it be done? It would have to be selective.

What is the TC of such a needle? 1us? What if we use a PI and sample for a 1us target and re-sample again 1us later. Subtract sample 2 from sample one.
We would get a good signal from a 1us sample and no signal from targets of 10us TC or more. It would be quite exclusive.

Is there a market for it?

My little self-stabbing episode has shown me how easy it is to get accidentally stabbed by a hypodermic needle.
These needles are extremely sharp.
I was lucky that it was a sterile needle, just out of the original sealed envelope.
What if it as a dirty needle thrown away by some junkie?
What if the needle was contaminated by HIV?

Are such needles to be found in public parks, children's playgrounds and near schools?

It would seem that it could be a marketable product.

Did we identify a new niche product and market?

Tinkerer

[sawmill]

WM6

The needle and the small gold thing are directly related for a
sensitivity test. I laid the answer out for you,but you completely
ignored it. High KHz = more sensitivity,hence will detect extremely
small objects,that a lower KHz machine can't hear.

Tinkerer
Yes the needle thing was started because of just what you described
in your last post. In some places those discarded needles are just as
deadly as land mines.

[Carl-NC]

Different stainless alloys have different levels of detectability, and higher frequencies do a better job of detecting them. It is likely you could create a specific s/s alloy which is entirely undetectable using induction methods.

Another detector challenge would be a high-security walk-through design. In prisons, they want to be able to detect a hypodermic needle hidden on a person's body walking through a 24" wide gate, at any angle. Or a small razor blade.

[Tinkerer]

WM6

The needle and the small gold thing are directly related for a
sensitivity test. I laid the answer out for you,but you completely
ignored it. High KHz = more sensitivity,hence will detect extremely
small objects,that a lower KHz machine can't hear.

Tinkerer
Yes the needle thing was started because of just what you described
in your last post. In some places those discarded needles are just as
deadly as land mines.

There are many gold detectors on the market. Difficult to find a niche worth wile the R&D.

However, if the needle problem is as big as some people say, it might just be the thing to do.

How many schools and sanitary authorities might want to buy a hypodermic needle detector to keep their places clean?

Tinkerer

[sawmill]

WM6

Just to see how the Pro pointer compares with a real probe
that is designed for very small objects,google Falcon MD 20.
The Falcon runs at 300 KHz,and is a real prospecting tool,and
for good reason.

Tinkerer
I don't know if a detector could be built for detecting needles,
that would be reliable enough for the purpose. But if it could,
there would be a big demand. As you discovered not all needles
are pure stainless steel. These are pretty easy to detect with
a good detector.

[Tinkerer]

Different stainless alloys have different levels of detectability, and higher frequencies do a better job of detecting them. It is likely you could create a specific s/s alloy which is entirely undetectable using induction methods.

Another detector challenge would be a high-security walk-through design. In prisons, they want to be able to detect a hypodermic needle hidden on a person's body walking through a 24" wide gate, at any angle. Or a small razor blade.

The good thing about needles or other minimum targets, is that is easy to build a detector that only detects very small targets and ignores large targets.

Or, at least so it would seem.

A 24" gate could be a challenge, but considering that my 18" coil detects a needle, there seems to be hope.

WM6 had the good idea to make the detector selective for needles. This has really helped to look in the right direction.

Tinkerer

[Tinkerer]

WM6

Just to see how the Pro pointer compares with a real probe
that is designed for very small objects,google Falcon MD 20.
The Falcon runs at 300 KHz,and is a real prospecting tool,and
for good reason.

Tinkerer
I don't know if a detector could be built for detecting needles,
that would be reliable enough for the purpose. But if it could,
there would be a big demand. As you discovered not all needles
are pure stainless steel. These are pretty easy to detect with
a good detector.

There are many grades of stainless steel. Some are non-magnetic to a higher degree than others. Some surgical tools are made of magnetic stainless steel, others not.

To make the matter more exciting, some stainless steels change the characteristic from n0n magnetic to magnetic after being stressed. Excessive stress causes stress corrosion and then the former non-magnetic stainless steel turns magnetic.

Obviously, the first thing to do is to take some non-magnetic needle and see if it can be detected.
Then define the detection parameters and design a prototype to find out where the problems are.

It is a long road, but all R&D is so.

Before going down that road, or rather climbing this steep hill, we need to find out a bit more about the problem.

So let's dig up some more information.

Tinkerer

[sawmill]

Tinkerer

Building a detector capable of finding those needles would be
the biggest challenge. For starters it would have to be immune to
EMI . It would have to have a reliable form of discrimination,because
where there is needles,there is also lots of metallic trash.Kind of like
finding a needle in a hay stack.

[Tinkerer]

OK, so I got my strongest magnet and went over all the different hypodermic needles.
None of the smallest ones actually stick to the magnet, but all can be turned around with the magnet, therefore they are all somewhat magnetic.

They are all made in China, as seems to be the way in this part of the world.

The smallest one, 1CC, #27Gx1/2" needle, the picture is attached, can be just detected with the 18" coil, but only presented flat, about 1/2 " from the coil winding. Using a long stick to present the target to the coil of course.

This circuit nor the coil have been designed for this purpose.
I am confident that I can design a detector that will detect these needles.

But, are there other needles that are harder to detect and in common use?

Tinkerer

[Tinkerer]

Tinkerer

Building a detector capable of finding those needles would be
the biggest challenge. For starters it would have to be immune to
EMI . It would have to have a reliable form of discrimination,because
where there is needles,there is also lots of metallic trash.Kind of like
finding a needle in a hay stack.

I think it will be easy to discriminate all larger trash and even fragments of foil. Very small gold nuggets might be a problem as I don't know a way to discriminate them.

The EMI is very high in my lab. This does not seem the problem.

Tinkerer