Amplifier frequency response

[baum7154]

The 6mm X 6mm target made from the top of the soda can in the second paragraph above had a thickness of .21mm or 2.1 times thicker than the 5mm X 5mm target made from the sidewall of the same can. The bottom of the same can is about three times thicker than the side wall. It measures .31mm

Dan

[green]

The 6mm X 6mm target made from the top of the soda can in the second paragraph above had a thickness of .21mm or 2.1 times thicker than the 5mm X 5mm target made from the sidewall of the same can. The bottom of the same can is about three times thicker than the side wall. It measures .31mm

Dan

[First of all it is quite difficult to accurately fabricate a 5mm X 5mm piece of Aluminum can side wall. I was able to make a 4.96mm X 4.99mm square, .10mm (.00393") thick target for this test. I had to hand file to the final 5mm dimensions using a fine cut jewelers file. I used a digital caliper to measure this target. reply315]

Wondering how size effects TC. Agree, cutting the correct size is difficult. I have a vernier caliper to measure things, so I couldn't check thickness. The other dimensions are close. It's easy to see the difference between 5x5 amd6x6mm. Haven't measured the effect on distance yet.

[green]

[First of all it is quite difficult to accurately fabricate a 5mm X 5mm piece of Aluminum can side wall. I was able to make a 4.96mm X 4.99mm square, .10mm (.00393") thick target for this test. I had to hand file to the final 5mm dimensions using a fine cut jewelers file. I used a digital caliper to measure this target. reply315]

Wondering how size effects TC. Agree, cutting the correct size is difficult. I have a vernier caliper to measure things, so I couldn't check thickness. The other dimensions are close. It's easy to see the difference between 5x5 amd6x6mm. Haven't measured the effect on distance yet.

Target amplitude vs distance for the four targets. RC feedback_.2usec

[Chet]

Hi Green
Thank you for this chart and the previous chart. They really do show how small changes in size and thickness can make big differences in detecting small objects.
Have a good day,
Chet

[6666]

First of all it is quite difficult to accurately fabricate a 5mm X 5mm piece of Aluminum can side wall.

Hi Dan
I made mine with eye ball accuracy with a workshop steel rule and the wall thickness was .1MM on digital callipers . Not a peep out of the TDI, which I know can detect a .2 Gram nugget.

[Chet]

Hi 6666
I cut a 0.25” x 0.25” (6.35mm) from the bottom of a coke can 0.26mm thick. My TDI detects it at approximately 3”. The same size from the side of the can (0.09mm) is not detected.
The TDI was set to min delay (10us) with ground balance off and max gain.
Have a good day,
Chet

[6666]

Hi 6666
I cut a 0.25” x 0.25” (6.35mm) from the bottom of a coke can 0.26mm thick. My TDI detects it at approximately 3”. The same size from the side of the can (0.09mm) is not detected.
The TDI was set to min delay (10us) with ground balance off and max gain.
Have a good day,
Chet

Hi Chet, thanks for that which coil are you useing ?

[Chet]

Hi Chet, thanks for that which coil are you useing ?

Hi 6666
I ran the test on the stock Dual Field and a Nugget Finder 8” x 6” Sadie and got the same results on both. I live in town so there is a lot of EMI. The test might be better in the field.
Have a good day,
Chet

[6666]

Hi Chet, well cut up a 1/4x1/4 bottom piece, .26mm thick and guess what detects no probs at 4-5 inches AIR TEST on my 14x7 nugget finder,
(checked the size of coil , called it a 14x9 somewhere else)
gain maxed, 10uS, GB off.
tested the 5mmx5mm .1MM again , not a peep, I dont think much of the TDI standard 12 inch mono coil, its good on coins but not very good on small stuff, rarely use it.
How would you rate the SADIE ?

[mickstv]

Hi 6666, when I set the first sample on my detector to 10us I can detect the 5x5mm at about 2cm, but if I reduce the first sample down to 8us delay the 5x5mm is detected at about 8cm.

[6666]

Hi Mick, thats a great result, you have a good MD design. Is that test with mono or DD ?

[Chet]

Hi Chet, well cut up a 1/4x1/4 bottom piece, .26mm thick and guess what detects no probs at 4-5 inches AIR TEST on my 14x7 nugget finder,
(checked the size of coil , called it a 14x9 somewhere else)
gain maxed, 10uS, GB off.
tested the 5mmx5mm .1MM again , not a peep, I dont think much of the TDI standard 12 inch mono coil, its good on coins but not very good on small stuff, rarely use it.
How would you rate the SADIE ?

Hi 6666
I use the Sadie on a GPX5000. It works well in close spaces. But I use a Nugget Finder 14” x 9” (outside measurements) almost all of the time. A friend has an older Nugget Finder coil that is narrower than mine. I have found it just as good as the Sadie on small targets and covers more ground. The GPX gets the ¼” bottom piece at slightly over 5”; here in town with the EMI screaming in my ears.
Have a good day,
Chet

[mickstv]

Hi Mick, thats a great result, you have a good MD design. Is that test with mono or DD ?

With the ML 11" DD coil.

I'll have to CRO the frontend of the detector again, but from memory I can sample down even earlier, maybe less than 7us. I couldn't do that with the mono coil detector with the blocking fet frontend.


EDIT the depth was on 5x5mm side wall coke can.

[mickstv]

Hi 6666
I use the Sadie on a GPX5000. It works well in close spaces. But I use a Nugget Finder 14” x 9” (outside measurements) almost all of the time. A friend has an older Nugget Finder coil that is narrower than mine. I have found it just as good as the Sadie on small targets and covers more ground. The GPX gets the ¼” bottom piece at slightly over 5”; here in town with the EMI screaming in my ears.
Have a good day,
Chet

Hi Chet, how deep can the 5000 detect 5x5mm side wall target using the 14x9 ?

Thanks
Mick

[baum7154]

[QUOTE=6666;216850]Hi Chet, well cut up a 1/4x1/4 bottom piece, .26mm thick and guess what detects no probs at 4-5 inches AIR TEST on my 14x7 nugget finder,
(checked the size of coil , called it a 14x9 somewhere else)
gain maxed, 10uS, GB off.
tested the 5mmx5mm .1MM again , not a peep
___________________________________

Hi Chet, 6666, & Mickstv

6666 your comment above about the 1/4" (6mm)target cut from the bottom piece being detected at 4 to 5" in air no problem is what I wonder if is in play with the detection of a roughly 6mm X 6mm target in air in the Felajoo video. Is it in fact made from the sidewall of an AL can or is it cut from the top or bottom of the can?

Other than to try to answer your question about "Whose detector can get the response from the 5mm X 5mm X .1mm sidewall?", the reason I posted the thickness data from the same AL can in post #15 above is because the response from the can bottom is much larger (10 times greater) than the response from the sidewall and I wanted to point that out. This may explain how the Felajoo was able to see a 6mm X 6mm target at 4" in the video. Is there another video out there that shows Felajoo detecting a 5mm X 5mm X .1mm target because I have not seen it? There seems to be a lack of clarity about Felajoo and its capabilities on small targets.

Mickstv, Thanks for the follow up on taking a close look at the 6mm X 6mm target in the video. It confirms that the target is not square and is most probably larger than 6mm X 6mm.

Regards,

Dan