Advanced PI coils

[Aziz]

Thanks 6666,

I'll try different diameter ratios. Could take a bit as the calculations need much more time this time.
Cheers,
Aziz,
curious too

[6666]

Hi IBgold
so you found the Omega (IB) coil no good for PI.
Do you think that the ratio's of the coils are wrong for PI ?
It will be interesting to see Aziz's results.

[IBGold]

I will be interested to see if Aziz's simulations confer with my testing of these coils for PI work I must add I was not suitably impressed to go any further.

Regards, Ian.

[6666]

Omega (IB) coil... you are the next candidate in my list..

In case you need the coil info.

[Aziz]

Upgrading Coil Software finished.

Hi all,

I've just finished coding the coil software to make me less work. I should have done this a long time ago .. anyway.

We can continue the comparison with the complex max. sensitivity region. I could provide the max. sensitivity for the reference mono coil regards to its edge region too (pin-pointing and max. near sensitivity region). A fair comparison of pin-pointing feature is possible now.

Omega (IB) coil... you are the next candidate in my list..

Cheers,
Aziz

[Aziz]

More Coil Analysis To Go

Hi all,

we aren't finished at all. There are more coil architectures to analyse and compare. Particularly the ones, which don't have a linear hot spot region/axis.
Particularly:
- Omega IB coil (this one is very interesting to compare)
- Figure-8 (different configuration)
- Tandem coils
..
It seems, I have to code my coil software to find the maximum response region. But this is an investment, which is very worth to do.

Aziz

[Sergey_P]

Very poor performer

Yes, moments mR+ and mR- very close
I did here such coil => http://www.md4u.ru/download/file.php?id=5970

[Aziz]

Hi Davor,

regarding the Davor-Sergey-Ppodg IB AI coil (the magnetic field strength cross-section coil configuration shown here earlier, named as "Davor-Sergey-Ppodg-CC-AI-Coil-01.jpg"):
Very poor performer (compared to the equivalent 10 inch mono coil).
At depth (30 inch): 100 (!) times lesser response compared to an equivalent mono coil

I made the 10 inch TX, 0.8 RX1, 0.4 RX2, 0.4 CX (4 mm apart from RX2) version:
At depth (30 inch): 50 (!) times lesser response compared to an equivalent mono coil

Compared to the co-axial offsetted larger RX coil version (without the CX coil), a definitely loser coil. The one I've shown without the CX coil is much better and easier to build.
At depth (30 inch, 0.71 version): 11.3 times lesser response compared to an equivalent mono coil
At depth (30 inch, 0.5 version, slightly thicker): 8.4 times

It doesn't really make sense to follow the CX versions IMHO. We have to wait for PJ making us a break-through proposal.

Cheers,
Aziz

[Aziz]

Going back to the Eric Foster type coaxial stacked coil which I used in the early 1980's in my PPD1 detector, there is another way of operating it. The centre coil is the TX, but is also RX1 so that it operates as a standard mono. This is fed to its own RX channel, sampled, differentially integrated and amplified such as to give an "all metal" signal. In the PPD1 this gave an audio only signal. RX2 and RX3 were similar size RX coils held in electronic balance. This fed a discriminator channel, sampled and integrated in the same way but displayed on a centre zero meter. The signal sample however was 4uS after TX switch ON. The differential earth's field sample was shared with the "all metal" channel. For non-ferrous metal the meter swung right and for ferrous it swung left. In air, this discrimination was very reliable, even steel washers and bottle caps showed as ferrous. This detector was primarily for beach searching and had no ground balance, hence inland it had limited use.

I used a Garrett 7in diameter stacked coil former as used in one of their VLF detectors at the time. The TX/RX1 acted as a standard 7in mono, and the RX2, RX3 balance coils were just for discrimination, but I was able to get almost the same detection range from the disc channel as the mono channel even though the spacing of RX2 and RX3 was only about 1.5in. The "all metal" channel had a comparator that switched on the disc. meter circuit when a few mV had been exceeded, so that noise did not appear on the meter in no signal conditions.

I will find the schematic of the disc channel and auto balance circuit in due course and post it on the Forum, unless it is there already - have to check.

Just another way of using the EF stacked coil, and with a good GB arrangement would have lots of potential. It would be interesting to try, say, 10in TX/RX1 with 7in RX2, RX3 for a nice coil shape that thins out toward the edge.

Eric.

Sure Eric. I can make a comparsion of whatever you prefer. But I'm trying to understand the coil you are describing. Maybe a better description of the coil or a sketch would help alot.

I'll describe the coil configuration what I've understood:
10in TX = RX1 (mono) placed in the middle of RX2 (near ground) and RX3 (above TX)
RX2, RX3 = 7in (anti-interference)
All coils co-axial arranged.
The co-axial distance (between RX2 and RX3): how many inches?
Did I understand it right?
If not, please give me more input data.

Cheers,
Aziz

[Aziz]

The original setup with Cx was fine. Without Cx a bit more interesting. Don't count it as failure, you just found a way not to do it

BTW, seeing PJ poisoning the well, you just know you are on the right track. A real ground balancing coil would surely make some more advanced rigs a bit less palatable considering their notoriously unpalatable price tags.

I'll try a bit more. The variation with a compensation coil compared to the others would be interesting however. And how it compares to the figure-8 types. You know, the figure-8 types lose a lot of depth too.

But I like equivalent RX+ and RX- coils (equivalent electrical characteristics). You will get much more with it.
Aziz

[Aziz]

Seems like all your great ideas are getting shot down. Especially your bad language. Can you not go a month without the filth?

PJ, do you have a good idea?
Oh yes, I forgot: You don't do anything for free...
How about 100 shares of "MadLabs Inc."(c)(r)(tm)?
*LOL*
Aziz

[Davor]

In air, this discrimination was very reliable, even steel washers and bottle caps showed as ferrous. This detector was primarily for beach searching and had no ground balance, hence inland it had limited use.

Eric, I'm about to try some more ideas in synthesizing a ferrous target for use with Spice. My current attempt is only half way there and I'd appreciate features to look after with ferrous targets excited by PI pulses so that I can verify Spice "targets" to qualify as Fe. Your solutions are very popular and vastly copied, yet my simulations showed that every delayed sampling is prone to Fe-NFe uncertainty and not so perfect discrimination, given the right combination of targets. Am I missing something?

Could you please teach us a bit on this, perhaps in a separate topic?

[Davor]

No, the above were the best I could get. All other trials produce a lot of zero's (super insensitive).

Anyone with a good idea?
Aziz

The original setup with Cx was fine. Without Cx a bit more interesting. Don't count it as failure, you just found a way not to do it

BTW, seeing PJ poisoning the well, you just know you are on the right track. A real ground balancing coil would surely make some more advanced rigs a bit less palatable considering their notoriously unpalatable price tags.

[Ferric Toes]

Going back to the Eric Foster type coaxial stacked coil which I used in the early 1980's in my PPD1 detector, there is another way of operating it. The centre coil is the TX, but is also RX1 so that it operates as a standard mono. This is fed to its own RX channel, sampled, differentially integrated and amplified such as to give an "all metal" signal. In the PPD1 this gave an audio only signal. RX2 and RX3 were similar size RX coils held in electronic balance. This fed a discriminator channel, sampled and integrated in the same way but displayed on a centre zero meter. The signal sample however was 4uS after TX switch ON. The differential earth's field sample was shared with the "all metal" channel. For non-ferrous metal the meter swung right and for ferrous it swung left. In air, this discrimination was very reliable, even steel washers and bottle caps showed as ferrous. This detector was primarily for beach searching and had no ground balance, hence inland it had limited use.

I used a Garrett 7in diameter stacked coil former as used in one of their VLF detectors at the time. The TX/RX1 acted as a standard 7in mono, and the RX2, RX3 balance coils were just for discrimination, but I was able to get almost the same detection range from the disc channel as the mono channel even though the spacing of RX2 and RX3 was only about 1.5in. The "all metal" channel had a comparator that switched on the disc. meter circuit when a few mV had been exceeded, so that noise did not appear on the meter in no signal conditions.

I will find the schematic of the disc channel and auto balance circuit in due course and post it on the Forum, unless it is there already - have to check.

Just another way of using the EF stacked coil, and with a good GB arrangement would have lots of potential. It would be interesting to try, say, 10in TX/RX1 with 7in RX2, RX3 for a nice coil shape that thins out toward the edge.

Eric.

[PATCHES JUNIOR]

Anyone with a good idea?
Aziz

Seems like all your great ideas are getting shot down. Especially your bad language. Can you not go a month without the filth?