NEW TECH PHOTOS

[Tinkerer]

In this thread I am going to show photos taken of the oscilloscope screen, with different targets.
The first 3 photos share the following parameters:
Oscilloscope settings:
Vertical = 200mV / div.
Horizontal = 1uS / div.
The photos show the output of the preamp, TAU TWO.
Preamp gain is 100
I will start with large targets
# 1 – No target
#2 - 5.5 Inch by 5.5 Inch by 0.375 Inch Aluminum plate, AG4 alloy at 30cm from the coil.
#3 – 6 pounder cannon ball from an 18th century shipwreck, about 3.5 “ diameter, at 30 cm from the coil.
# 4 Alu plate and cannon ball
As can be seen, this is not a good detector to look for cannon balls.

Tinkerer

[Tinkerer]

Response of small targets

Here is the set of small targets that I will show next.
It starts with a 1/2" square alu foil. this target has a TC of about 5uS.
With a gain of 100, this is the smallest target that shows with a Oscilloscope setting of 200mV / division.

Tinkerer

[Tinkerer]

Small targets

This whole test series was done with the same scope settings, the same gain and with the targets at the same place on the coil, with the exception of the cannon ball and the Aluminum plate, that were tested at 30 cm from the coil. Small targets:
Oscilloscope settings:
Vertical = 200mV / div.
Horizontal = 1uS / div.
The photos show the output of the preamp.
Preamp gain is 100
The targets are very close to the center of the coil, about 3mm above.
# 1 – No target
# 6 - Gold ring

The gold ring is very thin and made of 2 gold wires twisted together. It's weight is 0.5 grams.
It's TC is very short, so look for the signal at the beginning of the sampling window.

You can also see the PIVOT. The PIVOT is the place where the wave shape does not move. The first part of the wave shape goes up. the second halve of the wave shape goes down.
The PIVOT is at about 5uS, which roughly corresponds to the TC of the target.

Tinkerer

[Tinkerer]

Steel lug sample

For the next picture I have chosen the steel lug.
compared to the size of the gold ring it represents a much larger target.
Also it is a FE or magnetic target.
Note the difference in the response.

Tinkerer

[nick_f]

Hi Tinkerer,

Thank you for posting the photos.
The results are very promising and I would be very happy to get this sort of sensitivity and discrimination.
Do you know if the circuit gets affected by the ground? If this circuit is some sort of a hybrid, it may have some similar problems as VLF and may require GEB.

Is there any link to the construction of the coil you are using? I want to make one as well and do experiments.

Regards,
Nicolae

[Tinkerer]

Here is the set of small targets that I will show next.
It starts with a 1/2" square alu foil. this target has a TC of about 5uS.
With a gain of 100, this is the smallest target that shows with a Oscilloscope setting of 200mV / division.

Tinkerer

Here is the listing of the set of targets.

Small targets:
Oscilloscope settings:
Vertical = 200mV / div.
Horizontal = 1uS / div.
The photos show the output of the preamp.
Preamp gain is 100
The targets are very close to the center of the coil, about 3mm above.
# 1 – No target
#2 – 0.5” square alu foil
#3 – 1” square alu foil
#4 – 1”x2”sqare alu foil
#5 – 15mm x 10 mm steel lug from a roller bearing
# 6 – 0.5 gram gold ring
#7 – 0.55 gram silver ring
#8 – Penny – US$ 1c
#9 – Nickel – US$ 5c
#10 – Dime – US$ 10c
#11 – Quarter – US$ 25c
#12 – steel nail in the vertical position
#13 – 1 gram gold bar


Tinkerer

[Tinkerer]

Today I add target # 8. The silver ring.
It's weight is only 0.55 grams, but it is a very good conductor and the closed ring shape is perhaps the best target shape.
It's TC is more than 10uS so the PIVOT is outside the sampling window.

Note the difference of response between the target # 5, the steel lug.

Tinkerer

[porkluvr]

Tinkerer, I get a lot out of your scope shots but I would like to make a suggestion. If you have more than one or two fotos in a batch, is it possible to number (or label) your photos so that we can more easily reference back to your index numbers or description? * (I guess it's too late now).

I may download these and imprint some descriptive text on them for my future reference.

Anyway, thanks for the shots. This kind of stuff has been pretty much ignored in the past.


*Oh, and I'd like french fries with that.

edit: Really you should probably ignore my suggestion. I'll trust you not to mix the fotos up, and make my own captions.

[Tinkerer]

Tinkerer, I get a lot out of your scope shots but I would like to make a suggestion. If you have more than one or two fotos in a batch, is it possible to number (or label) your photos so that we can more easily reference back to your index numbers or description? * (I guess it's too late now).

I may download these and imprint some descriptive text on them for my future reference.

Anyway, thanks for the shots. This kind of stuff has been pretty much ignored in the past.


*Oh, and I'd like french fries with that.

edit: Really you should probably ignore my suggestion. I'll trust you not to mix the fotos up, and make my own captions.

You are very much right.
I started to write a legend on each, but had to go and see to some urgent job and forgot. My photo files are named, but the names do not come out on the post.

I appreciate your feedback.

All the best

Tinkerer

[nick_f]

Today I add target # 8. The silver ring.
Tinkerer

Hi Tinkerer,

The silver ring is target # 7. It would be ideal if the "no target response" could be superimposed with a different colour on each target photo.

Regards,
Nicolae

[Tinkerer]

Here is the response of the Penny, a US$ 1c coin.
This is # 8
A penny has a TC of about 70uS, so the PIVOT is not in the sampling window. Rather the whole waveform has gone about 300mV more positive.

Note that the total gain for all these pictures is only 100

Tinkerer

[Tinkerer]

Hi Tinkerer,

The silver ring is target # 7. It would be ideal if the "no target response" could be superimposed with a different colour on each target photo.

Regards,
Nicolae

Ho Nicolae,

Oops, thank you for correcting the mistake.

How do you do the superposition?

I have also higher resolution pictures they are 1400 pixel wide, but my internet connection is slow for the uploading.

Tinkerer

[nick_f]

Ho Nicolae,

How do you do the superposition?

Tinkerer

Hi Tinkerer,

Somebody with experience with Photoshop or other graphic programs could do it very fast. It involves working with different layers and adding one on top of the other.
I already did that and I sent the sample images to Tinkerer, for evaluation.

Regards,
Nicolae

[Tinkerer]

#9, the Nickel or US$ 5c. This coin is larger and thicker than the Penny, but is of a Copper-Nickel alloy that give it a short TC of about 20uS.
The Penny, by the way is copper clad zinc.
On the Nickel you can again see the PIVOT, the waveform goes up at the beginning and down at the end.

I also found the precise alloy of the US$ coins. It is interesting to see how a very small difference in the amount of nickel in the alloy, makes a big difference in the signal response.

The problem with all these targets is the difference in shape. The shape makes a big difference in the response.

Tinkerer

[Noemio]

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