Hypodermic needles

[Qiaozhi]

I did some air tests tonight using the needles received from Nupi (plus a small square of aluminium cola can - 5mm square). The bottom line is that none of the detectors I tested could detect any of the needles.

The detectors used were:
Laser Hawkeye
Garrett GTX1000
Nexus Credo
Tesoro Bandido
Minipulse Plus
Crossbow Classic PI
Prototype PI

Only the Hawkeye, GTX1000, Credo and Bandido could detect the small piece of aluminium can.
However, I'm not surprised that the PIs were unable to see it, as they're designed for beach and relic hunting. The prototype PI has a bipolar transmitter and an 8us sample delay, and even that was unable to detect it.

VLF detectors are generally more sensitive to small metal targets than PIs (which rely totally on detecting the eddy currents in the target). Since the target is very small, the eddy currents have substantially died away before you can take a sample. Whereas a VLF detector continuously stimulates the target, and is able to receive a stronger signal than the PI. On the hand PIs can have a distinct advantage in mineralised ground, and don't lose as much depth between an air and a field test.

For detecting very small targets, a VLF is definitely the best choice (if the ground is not mineralised) probably with a high TX frequency, and a small coil.

Nupi - Thanks again for the needles. They will make some good test targets for future projects.

[6666]

The prototype PI has a bipolar transmitter and an 8us sample delay,

Is this only a private project ?

[Qiaozhi]

Is this only a private project ?

Yes - it is not for public consumption.

[WM6]

Additionally tested Detech EDS Reacher (intended to be prospecting tool) equipped with two DD coils small 8x6" and standard 9x9". It can detect 0.1gram gold nugget at about 1" deep in mineralized testing substrate, but not hypo-needle, nor on surface nor in air (touching coil).

[Nupi]

I did some air tests tonight using the needles received from Nupi (plus a small square of aluminium cola can - 5mm square). The bottom line is that none of the detectors I tested could detect any of the needles.

The detectors used were:
Laser Hawkeye
Garrett GTX1000
Nexus Credo
Tesoro Bandido
Minipulse Plus
Crossbow Classic PI
Prototype PI

Only the Hawkeye, GTX1000, Credo and Bandido could detect the small piece of aluminium can.
However, I'm not surprised that the PIs were unable to see it, as they're designed for beach and relic hunting. The prototype PI has a bipolar transmitter and an 8us sample delay, and even that was unable to detect it.

VLF detectors are generally more sensitive to small metal targets than PIs (which rely totally on detecting the eddy currents in the target). Since the target is very small, the eddy currents have substantially died away before you can take a sample. Whereas a VLF detector continuously stimulates the target, and is able to receive a stronger signal than the PI. On the hand PIs can have a distinct advantage in mineralised ground, and don't lose as much depth between an air and a field test.

For detecting very small targets, a VLF is definitely the best choice (if the ground is not mineralised) probably with a high TX frequency, and a small coil.

Nupi - Thanks again for the needles. They will make some good test targets for future projects.

I appreciate your effort taken.
This gives me a stimulance to proceed my project.
Now I'm sure I'm on the right track.

[Nupi]

Additionally tested Detech EDS Reacher (intended to be prospecting tool) equipped with two DD coils small 8x6" and standard 9x9". It can detect 0.1gram gold nugget at about 1" deep in mineralized testing substrate, but not hypo-needle, nor on surface nor in air (touching coil).

By doing both the test you have helped me a lot. I had never compare so many different MD.
Thanks!!!


I'm going this afternoon post some videos.

[Nupi]

These tests were to adjust the box with the small coil.
So if you can hear the box was not adjust quite right.

[Qiaozhi]

Some additional info:
Just tested a Whites Bullseye II pinpointer, and it can detect the small square of aluminium at 7mm, but there's nothing from the needles.

[Nupi]

Some additional info:
Just tested a Whites Bullseye II pinpointer, and it can detect the small square of aluminium at 7mm, but there's nothing from the needles.

I have the aluminum plate not tested yet with the nupi-pp.
With the nupi-pp I can not detect hyp-needles.
But in fact, you can not detect hypo-needle with a pp.(I think)

[Nupi]

Now I have the Smart further changed and can now work reasonably without the box.
This is the first video of the Smart without box. It is intended to test the disc.
The intention is to discriminate the beach sand and a rusty nail and other targets still able to detect.

[Nupi]

[QUOTE=Nupi;193861]These tests were to adjust the box with the small coil.
So if you can hear the box was not adjust quite right.QUOTE]

Link was broken, these works.

[green]

Plotted some more data. 5x5mm and 2x2mm cut from an aluminum can. Cut 7 mm off the hypodermic needle, .89mm x 32mm. The data isn't as clean as reply #53. I'm always changing things, guess I made things worse. Shouldn't effect time constant, reply #53 the scope trigger had a resistor in series making it look like the amplifier was coming out of saturation 500nsec sooner than it was. Cut the 2x2 aluminum can to see if I could make a target similar to my hypodermic needle, still has a longer time constant and more signal. The needle I'm using is larger than the needles Nupi is using. Tried to get some needles, they don't sell without a prescription. With the needles being smaller I don't know if I could plot them anyway.
The 5x5mm target was 10mm above first winding not 5mm as listed on the chart.

[Nupi]

Plotted some more data. 5x5mm and 2x2mm cut from an aluminum can. Cut 7 mm off the hypodermic needle, .89mm x 32mm. The data isn't as clean as reply #53. I'm always changing things, guess I made things worse. Shouldn't effect time constant, reply #53 the scope trigger had a resistor in series making it look like the amplifier was coming out of saturation 500nsec sooner than it was. Cut the 2x2 aluminum can to see if I could make a target similar to my hypodermic needle, still has a longer time constant and more signal. The needle I'm using is larger than the needles Nupi is using. Tried to get some needles, they don't sell without a prescription. With the needles being smaller I don't know if I could plot them anyway.
The 5x5mm target was 10mm above first winding not 5mm as listed on the chart.

Interesting tests.
You have perseverance and I like that.
I'll send you a PM.

[6666]

Yes - it is not for public consumption.

Thanks.

[WM6]

The intention is to discriminate the beach sand and a rusty nail and other targets still able to detect.

Very convincing wet sand and ferro part discrimination and still hypo-needle detection. Did you use salt water?