Pinpointer coil design

[fixstuff]

Hello,

I have a question. For a pinpointer coil design, what is typically the best way to implement this? Would the design be similar to a traditional coil, just with a small diameter?

I am looking at a design that will have multiple, very small coils located next to each other for receive, all located inside the diameter of a large, square, rectangular transmit coil. I am hoping this would give me a lot of depth, and a highly localized pinpoint capability.

I don't care for discrimination capabilities, but would be looking for all metal, high sensitivity.

My current plan is to have a large coil wound on a long rectangular form, with smaller coils embedded in the form. I would be switching the receiver circuit to each of the various RX coils in sequence.

What's the best all metal technology? BFO? IB? PI?

Any ideas and tips are appreciated.

[kt315]

hi, did you see this promo video in youtube about Garrett tech and there is their pro pinpointer too? good look how it made... IMO. a clip is from DISCOVERY channel.

[Carl-NC]

What you are proposing is difficult with IB, as each RX coil would need to be individually balanced. You could still do it CW without IB, by just going straight to demod. PI would be much easier. This happens to be how many security walk-through detectors are designed.

However, depth is mostly relative to the RX coil size, so by shrinking it down to, say, 1 inch your depth will be about 2 inches. And by time-sharing your RX processing amongst multiple channels, you lose even more depth. Security walk-throughs have a dedicated RX circuit on every RX coil.

[fixstuff]

Thanks for the reply, ok, PI it is. If I pulsed the transmit coil once for every rx coil sample, I wouldn't have to time share I don't believe right? To get the depth, If I went with a really low frequency, and a lot of power, would this give me more depth to work with?

[Carl-NC]

Ideally, every time you pulse the TX, you want to sample all the RX coils simultaneously. And you want to run the whole system as fast as you can. More samples increase correlated signals (targets) and decrease random signals (noise) for a win-win scenario. Lots of power helps, too.

[mikebg]

hi, did you see?... .

Did you see the most suitable hardware?

[kt315]

I noticed there is simple KIT project on feepay. good for start.

http://www.ebay.com/itm/Metal-Detect...90557698191%26

[6666]

They even give the cct

[fixstuff]

Actually that is perfect for my project! It looks like I can interface right into the circuit board also. More depth would be a bit nicer, but I might be able to live with the claimed depth.

[fixstuff]

Looking at this pinpointer box, the coil is done right on the circuit board. Would it be possible to be a larger version of a standard MD coil on a circuit board? Has any manufacturer done this? This seems like you could really step up coil build repeatability with this.