Advanced PI coils

[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

[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]

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]

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

[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]

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

[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

[6666]

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

In case you need the coil info.

[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]

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.

[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

[Sergey_P]

[Aziz]

Preliminary Omega Coil Comparison Result

This is the Omega IB coil vs. mono coil. Hey, it's performing better than DD-IB coil.

BX/BU: Bucking coil 0.4 times TX diameter
RX: Receive coil 0.5 times TX diameter
Interestingly, the hot spot axis remains almost at the center axis (approx. -1 cm +/- 5mm from the center position of the TX).

Ok, I've added DD-IB, CC-IB (0.5RX) to the comparision too.

Coil Comparison (Calculated Response Ratio to Reference Coil)
© 2012 by Aziz Ögüt. All Rights Reserved. 20-Dec-2012
Reference Coil: 300 µH Round Mono Loop Coil
		10" Double-D Induction Balanced Round Coil	10" Concentric Co-planar Induction Balanced Round Coil (0.5)	10" Omega-IB (0.4BX, 0.5RX)
Target Depth [inch]	Target Depth [cm]	Relation to Reference	Relation to Reference	Relation to Reference
1	2,5	2,188	3,510	6,494
2	5,1	0,973	3,245	2,914
3	7,6	0,771	2,631	1,936
4	10,2	0,703	2,126	1,511
5	12,7	0,673	1,786	1,275
6	15,2	0,657	1,563	1,131
7	17,8	0,647	1,414	1,038
8	20,3	0,641	1,310	0,975
9	22,9	0,636	1,236	0,931
10	25,4	0,633	1,182	0,899
11	27,9	0,631	1,140	0,875
12	30,5	0,629	1,108	0,857
13	33,0	0,628	1,083	0,843
14	35,6	0,627	1,063	0,831
15	38,1	0,626	1,047	0,822
16	40,6	0,625	1,033	0,815
17	43,2	0,625	1,022	0,809
18	45,7	0,624	1,012	0,804
19	48,3	0,624	1,004	0,800
20	50,8	0,624	0,997	0,796
21	53,3	0,623	0,991	0,793
22	55,9	0,623	0,985	0,791
23	58,4	0,623	0,981	0,789
24	61,0	0,623	0,977	0,787
25	63,5	0,622	0,973	0,785
26	66,0	0,622	0,970	0,784
27	68,6	0,622	0,967	0,782
28	71,1	0,622	0,964	0,781
29	73,7	0,622	0,962	0,780
30	76,2	0,622	0,960	0,779

Now let's look, whether we can get a better Omega coil.

Cheers,
Aziz

[Aziz]

Omega IB Coils vs. Mono Coil

This is a comparison between different diameter ratios of BX (small inner part of TX, kind of bucking coil) and RX of an Omega IB Coil vs. a mono coil. The 0.33 diameter variant (0.33BX, 0.33RX) perform a bit better (less noise, better SNR, better pin-pointing).
Indeed, not that bad for it's simplicity compared to a DD IB coil.

Coil Comparison (Calculated Response Ratio to Reference Coil)
© 2012 by Aziz Ögüt. All Rights Reserved. 20-Dec-2012
Reference Coil: 300 µH Round Mono Loop Coil
		10" Omega-IB (0.4BX, 0.5RX)	10" Omega-IB (0.4BX, 0.33RX)	10" Omega-IB (0.5BX, 0.5RX)	10" Omega-IB (0.33BX, 0.33RX)
Target Depth [inch]	Target Depth [cm]	Relation to Reference	Relation to Reference	Relation to Reference	Relation to Reference
1	2,5	6,494	14,723	6,822	14,584
2	5,1	2,914	5,361	2,905	5,513
3	7,6	1,936	3,003	1,841	3,110
4	10,2	1,511	2,058	1,398	2,139
5	12,7	1,275	1,594	1,165	1,661
6	15,2	1,131	1,337	1,026	1,397
7	17,8	1,038	1,181	0,937	1,237
8	20,3	0,975	1,080	0,876	1,134
9	22,9	0,931	1,011	0,834	1,063
10	25,4	0,899	0,962	0,804	1,014
11	27,9	0,875	0,926	0,781	0,977
12	30,5	0,857	0,899	0,763	0,950
13	33,0	0,843	0,878	0,750	0,929
14	35,6	0,831	0,861	0,739	0,912
15	38,1	0,822	0,848	0,730	0,899
16	40,6	0,815	0,837	0,723	0,888
17	43,2	0,809	0,828	0,717	0,880
18	45,7	0,804	0,821	0,712	0,872
19	48,3	0,800	0,815	0,708	0,866
20	50,8	0,796	0,810	0,705	0,861
21	53,3	0,793	0,805	0,702	0,857
22	55,9	0,791	0,801	0,699	0,853
23	58,4	0,789	0,798	0,697	0,850
24	61,0	0,787	0,795	0,695	0,847
25	63,5	0,785	0,793	0,694	0,844
26	66,0	0,784	0,790	0,692	0,842
27	68,6	0,782	0,789	0,691	0,840
28	71,1	0,781	0,787	0,690	0,839
29	73,7	0,780	0,785	0,689	0,837
30	76,2	0,779	0,784	0,688	0,836

Notice: The comma should be a decimal dot of course. This is due to internationalisation.

Next: Let's compare the CC-IB-AI coil against the Tophat IB AI coil. The CC-IB-AI contains another RX- coil co-axial above the coil arrangement of the standard CC-IB coil.

Cheers,
Aziz

[Aziz]

CC IB AI Coil vs. Tophat IB AI Coil vs. Mono Coil

This is the concentric co-planar IB AI coil (CC IB AI) comparison against the other ones. The CC IB AI coil has additional a RX- coil, placed co-axial above the standard concentric co-planar IB coil to get the AI feature.
Which is going to make the running?
CC IB AI or Tophat IB AI coil?

See yourself below.
(I hope, the wide excel table fits into the forum page.)

Coil Comparison (Calculated Response Ratio to Reference Coil)
© 2012 by Aziz Ögüt. All Rights Reserved. 20-Dec-2012
Reference Coil: 300 µH Round Mono Loop Coil
		10" Tophat 0.5 CC IB AI Coil (5 inch distance)	10" Tophat 0.5 CC IB AI Coil (10 inch distance)	10" Tophat 0.33 CC IB AI Coil (5 inch distance)	10" Tophat 0.33 CC IB AI Coil (10 inch distance)	10" CC IB AI (0.5, 5 inch co-axial distance)	10" CC IB AI (0.5, 10 inch co-axial distance)	10" CC IB AI (0.33, 5 inch co-axial distance)	10" CC IB AI (0.33, 10 inch co-axial distance)
Target Depth [inch]	Target Depth [cm]	Relation to Reference	Relation to Reference	Relation to Reference	Relation to Reference	Relation to Reference	Relation to Reference	Relation to Reference	Relation to Reference
1	2,5	6,412	6,636	17,376	17,663	4,100	3,703	12,702	11,401
2	5,1	4,374	4,581	8,267	8,537	3,314	3,231	7,198	7,101
3	7,6	2,978	3,176	4,468	4,714	2,479	2,537	4,143	4,274
4	10,2	2,169	2,364	2,849	3,081	1,897	2,013	2,711	2,892
5	12,7	1,696	1,891	2,057	2,281	1,523	1,666	1,981	2,177
6	15,2	1,401	1,598	1,616	1,838	1,278	1,436	1,567	1,769
7	17,8	1,205	1,406	1,343	1,566	1,109	1,278	1,307	1,515
8	20,3	1,066	1,271	1,161	1,385	0,987	1,164	1,132	1,344
9	22,9	0,962	1,172	1,030	1,256	0,894	1,079	1,006	1,222
10	25,4	0,882	1,095	0,932	1,160	0,822	1,012	0,911	1,130
11	27,9	0,818	1,034	0,855	1,085	0,763	0,957	0,837	1,058
12	30,5	0,765	0,984	0,793	1,025	0,714	0,912	0,776	1,000
13	33,0	0,720	0,942	0,742	0,974	0,672	0,873	0,726	0,951
14	35,6	0,681	0,905	0,698	0,932	0,636	0,839	0,684	0,909
15	38,1	0,647	0,872	0,660	0,894	0,605	0,809	0,647	0,873
16	40,6	0,617	0,843	0,627	0,862	0,577	0,782	0,614	0,841
17	43,2	0,591	0,817	0,598	0,832	0,552	0,758	0,586	0,812
18	45,7	0,567	0,793	0,572	0,805	0,529	0,735	0,560	0,786
19	48,3	0,545	0,771	0,549	0,781	0,508	0,714	0,537	0,762
20	50,8	0,525	0,751	0,527	0,759	0,489	0,695	0,516	0,740
21	53,3	0,506	0,731	0,508	0,738	0,472	0,677	0,497	0,720
22	55,9	0,489	0,714	0,490	0,719	0,456	0,660	0,479	0,701
23	58,4	0,473	0,697	0,473	0,701	0,441	0,644	0,463	0,683
24	61,0	0,458	0,681	0,458	0,684	0,427	0,629	0,448	0,666
25	63,5	0,445	0,666	0,443	0,667	0,414	0,615	0,434	0,651
26	66,0	0,432	0,651	0,430	0,652	0,402	0,601	0,421	0,636
27	68,6	0,420	0,638	0,417	0,638	0,391	0,588	0,408	0,622
28	71,1	0,408	0,625	0,406	0,624	0,380	0,576	0,397	0,608
29	73,7	0,397	0,612	0,395	0,611	0,370	0,564	0,386	0,595
30	76,2	0,387	0,600	0,384	0,599	0,360	0,553	0,376	0,583

The Tophat(c)(r)(tm)(free) coil is "World's best IB AI coil design"(c)(r)(tm)(free). Probably until someone comes with a break-through coil idea.

Cheers,
Aziz