Hi Eric! Sampling circuits

[Wirechief]

Ok Carl thanks for the explanation again and I have been scrounging around at work and finding some older( early 90's) books from Maxim and Analog Devices and am scarfing up the info in them. Maybe the Engineers won't miss them too much haha! Ok on your Beachscan and I wonder what controls are on your model? I'll check out that book link to see if I can find some good stuff.
You know Carl I have been thinking about these coils on the detectors and there has got to be a way to make them even better. The coil is really 9/10ths of the system and if someone can improve upon that part I think we would see a huge step up in performance. What I wonder about is how much of the electromagnetic field actually goes into the ground and how much goes out to the sides and top of the coil. Seems like a lot of energy might be wasted and if we could direct most of it into the ground, sort of like a beam antenna does on radio it could increase the depth and sensitivity greatly. Of course this is wishful thinking or not thinking correctly maybe, I don't know. Ok Carl I will CU later my friend and I'm sure I will come up with more questions. God Bless ya! John the Wirechief.

 

[Prospector Al]

Hi Wirechief,
You were wondering about me...I've been in Texas of all places, and I almost called you to see if I could pay you a visit. (I was in Austin.) Regarding the advances in technology: It's easy to have ideas, but some of them don't pan out. I'm in the process of trying some new ideas that look good on paper. Often, unexpected difficulties arise when you implement a "good idea". I'll keep you posted...

However, Marconi was able to send signals at 50 kHz over a few thousand miles, so shouldn't it be possible to detect the re-radiated signal from a gold nugget at a few feet?
Prospector Al

 

[Wirechief]

Wow how are you Al !? Good to hear from you. Oh man you should have come by and visited with the wife and I. Of course you might have to put up with a couple of backwoods hicks like us haha! You bet I think you can detect gold with a return signal in the microvolts range and keep going deeper, just have to try something new and different. I just wish we had gold nuggets here in the farm fields to detect. By all means keep me in the news on your experiments and let me know how you do. But you are right what we think is a great idea ends up in the shredder sometimes. But we just have to keep going. I remember one night I was on 80 meter CW and running 10 watts on a multiband vertical and a fellow answered my CQ. We gave each other the same 10 over S9 signal report and he was running a kilowatt. So big power doesn't always mean your king of the hill. Well really good to hear from you Al and come back more often and teach us something about all this stuff. God Bless ya my friend and 73 de John the Wirechief.

 

[Eric Foster]

Hi All,

This is an interesting thread that happened while I was away sunning myself on a distant beach. No I didn't take a metal detector

So far, I have always used synchronous sampling for PI's. I have tried different variations on the theme, but find that I get the best results with relatively simple circuitry. Faster logic, faster gates, micros, etc. often result in more noise problems both for em affecting the detector, and the detector radiating unwanted em. After all, I can sample at 1uS delay with fairly standard circuits and that is way beyond what a treasure detector could use except maybe in bone dry coral sand.

I have tended to concentrate more on coil design and coil shielding, plus analog noise filtering after the sampling and integrating. I tried a dc accurate digital filter once, but ran into noise problems and gave up on it. I'm sure an all digital PI will come in the future, as it has in geophysical instrumentation, but my world is analog. Love my vinyl records and tube amplifier

Eric.

 

[Wirechief]

Welcome back Eric and thanks for the response. Although we all know that everything pretty much will be digitized someday I like you still like vacuum tubes and morse code. I believe that the coil is where a lot of experimenting can be done which is 9/10th's of the system. But the sampling question came to my mind and I am going to read all I can on sampling circuits and noise. These digital circuits can be very noisy and I'm sure it is difficult to design a digital detector. So I will talk to you later Eric and God Bless ya! John the Wirechief.