Advanced PI coils

[Tinkerer]

Aziz,

thank you for the excellent tables.
I have one question:
With the 0.33 RX coil, the response at the very center is very good. Good for pinpointing. How does the reception compare more to the side, under the TX?

With my coplanar concentric IB coil, (0.5) I can not see much difference from a mono coil, in the RX area. It is of course deeper at the very center, but, there are differences in the RX area of different coil configurations.

Some configurations like the spiral coils, have a more funnel like shape.
Some configurations are more of a conic shape.
Still other configurations produce a more half sphere shape.
And of course, the DD coils produce a more spade like shape.

Is it possible to get a reference number for a point at, lets say, r0.7 with the same depths and coils?

[Ferric Toes]

I'll add more coil comparisons from time to time. Don't blame me for being lazy. I haven't finished all configurations yet. But before the doomsday gets in action, you should simply know it.
Cheers,
Aziz

Don't worry about Doomsday. There is a parallel universe where the earth isn't destroyed and us with it. We will just carry on there. Maybe though, you won't have developed the coil software in that one , or.....perhaps its best not to speculate.

Eric

[Aziz]

I'll add more coil comparisons from time to time. Don't blame me for being lazy. I haven't finished all configurations yet. But before the doomsday gets in action, you should simply know it.
Cheers,
Aziz

[Aziz]

Co-Axial IB AI Coil vs. Mono Coil

Definitely a loser coil configuration. But you can crank up the gain as an EMI noise rejection is there (AI, IB configuration).
The co-axial distance is referring to RX+ and RX- distance. The TX coil is placed in the mean co-axial distance.

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" Co-axial IB AI Coil (5 inch distance)	10" Co-axial IB AI Coil (7.1 inch distance)	10" Co-axial IB AI Coil (10 inch distance)
Target Depth [inch]	Target Depth [cm]	Relation to Reference	Relation to Reference	Relation to Reference
1	2,54	0,414	0,358	0,253
2	5,08	0,385	0,322	0,227
3	7,62	0,368	0,305	0,218
4	10,16	0,361	0,303	0,221
5	12,70	0,360	0,307	0,230
6	15,24	0,362	0,315	0,243
7	17,78	0,365	0,325	0,257
8	20,32	0,368	0,334	0,271
9	22,86	0,370	0,342	0,284
10	25,40	0,370	0,350	0,297
11	27,94	0,370	0,356	0,309
12	30,48	0,368	0,360	0,319
13	33,02	0,366	0,364	0,329
14	35,56	0,363	0,367	0,337
15	38,10	0,360	0,368	0,344
16	40,64	0,356	0,369	0,349
17	43,18	0,352	0,369	0,354
18	45,72	0,347	0,368	0,358
19	48,26	0,342	0,367	0,362
20	50,80	0,337	0,365	0,364
21	53,34	0,332	0,363	0,366
22	55,88	0,327	0,360	0,367
23	58,42	0,322	0,357	0,368
24	60,96	0,317	0,354	0,368
25	63,50	0,312	0,351	0,368
26	66,04	0,307	0,348	0,368
27	68,58	0,302	0,345	0,367
28	71,12	0,297	0,341	0,366
29	73,66	0,292	0,337	0,365
30	76,20	0,288	0,334	0,363

Cheers,
Aziz

[Aziz]

See Where The Magic is Buried.

Now the TX/RX (separate) concentric co-planar PI coils (not IB, not AI!) vs. mono loop round coil (reference).
(Target height means target depth of course. And I have compressed the figures a bit).
Can you see now, where the benefit regards to SNR is?

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" TX/RX CC PI Coil (0.71RX)	10" TX/RX CC PI Coil (0.5RX)	10" TX/RX CC PI Coil (0.33RX)
Target Depth [inch]	Target Depth [cm]	Relation to Reference	Relation to Reference	Relation to Reference
1	2,54	2,687	6,809	17,851
2	5,08	2,328	4,723	8,667
3	7,62	1,984	3,302	4,825
4	10,16	1,722	2,486	3,188
5	12,70	1,537	2,015	2,394
6	15,24	1,408	1,729	1,960
7	17,78	1,318	1,546	1,699
8	20,32	1,254	1,423	1,531
9	22,86	1,206	1,337	1,417
10	25,40	1,171	1,274	1,336
11	27,94	1,143	1,228	1,276
12	30,48	1,122	1,192	1,231
13	33,02	1,105	1,164	1,196
14	35,56	1,091	1,141	1,168
15	38,10	1,080	1,123	1,146
16	40,64	1,070	1,108	1,128
17	43,18	1,062	1,096	1,113
18	45,72	1,056	1,086	1,100
19	48,26	1,050	1,077	1,089
20	50,80	1,045	1,069	1,080
21	53,34	1,041	1,063	1,073
22	55,88	1,038	1,057	1,066
23	58,42	1,034	1,052	1,060
24	60,96	1,032	1,048	1,055
25	63,50	1,029	1,044	1,050
26	66,04	1,027	1,041	1,046
27	68,58	1,025	1,038	1,043
28	71,12	1,023	1,035	1,039
29	73,66	1,022	1,033	1,036
30	76,20	1,020	1,031	1,034

Cheers,
Aziz

[Aziz]

Just trying to import an excel table.
The comparison of DD, CC-IB coils vs. Mono 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" Double-D Induction Balanced Round Coil	10" Concentric Co-planar Induction Balanced Round Coil (0.71)	10" Concentric Co-planar Induction Balanced Round Coil (0.5)	10" Concentric Co-planar Induction Balanced Round Coil (0.33)
Target Height [inch]	Target Height [cm]	Relation to Reference	Relation to Reference	Relation to Reference	Relation to Reference
1	2,54	2,188416159928	1,148678006070	3,510437123387	11,089712087054
2	5,08	0,972511068638	1,204063505976	3,245496903647	7,423966698251
3	7,62	0,770966888031	1,188203670416	2,630620755321	4,544423289360
4	10,16	0,703490989184	1,132981339100	2,125593485935	3,099995736055
5	12,70	0,672945369395	1,072594806991	1,785843283318	2,355435268466
6	15,24	0,656588092772	1,020408053517	1,563019831856	1,937082124269
7	17,78	0,646827021344	0,978685682673	1,413674344856	1,682389912558
8	20,32	0,640541487804	0,946104905114	1,310248945149	1,516846098887
9	22,86	0,636258381621	0,920704248993	1,236240190892	1,403476403014
10	25,40	0,633209319245	0,900751932661	1,181686669445	1,322514871565
11	27,94	0,630961880593	0,884903599264	1,140414277387	1,262694987726
12	30,48	0,629257682505	0,872159682506	1,108476339790	1,217238035179
13	33,02	0,627934656283	0,861785934682	1,083272314032	1,181875430389
14	35,56	0,626886967125	0,853242338863	1,063039723596	1,153813519610
15	38,10	0,626043138116	0,846128820964	1,046553178052	1,131162722723
16	40,64	0,625353461809	0,840145969769	1,032940917669	1,112608180230
17	43,18	0,624782538635	0,835067220827	1,021569868323	1,097212140505
18	45,72	0,624304549526	0,830719122446	1,011971700257	1,084291207156
19	48,26	0,623900379851	0,826967391279	1,003794106539	1,073337745958
20	50,80	0,623555513975	0,823707004952	0,996768154069	1,063968300589
21	53,34	0,623258949522	0,820854945229	0,990685684739	1,055888788162
22	55,88	0,623002005597	0,818344834184	0,985383511654	1,048870543520
23	58,42	0,622777948145	0,816123384089	0,980732404757	1,042733742448
24	60,96	0,622581481615	0,814147223701	0,976628822622	1,037335016649
25	63,50	0,622408119829	0,812380729063	0,972988917433	1,032559323038
26	66,04	0,622254308405	0,810794747095	0,969744812502	1,028313264207
27	68,58	0,622117425818	0,809364876014	0,966840129024	1,024520267225
28	71,12	0,621994844384	0,808070905988	0,964228598593	1,021117212401
29	73,66	0,621884963684	0,806895318451	0,961871364484	1,018052146109
30	76,20	0,621785807492	0,805824442582	0,959736304890	1,015280744043

Let's see, whether it works...

Yup!, seems to work.
A ratio > 1 means: performing better than the reference coil regards to SNR.
A ratio < 1 means: performing worser than the reference coil regards to SNR.

The ratio is the relation of induced target response voltage of the specified coil vs. reference coil.

Aziz

[Ferric Toes]

Hi Eric,
Regarding your former question:
The ground response will be reduced due to apparent (!) smaller and separate RX coil. However, we are thinking of making the smaller RX coil with more turns count (more inductivity) to get an equivalent EMI noise induction compared to the larger RX coil (the 10 inch 300 µH RX = mono PI coil as the reference). As a consequence of this, we have again more ground response near the RX coil region. BTW, we have an excellent pin-pointing and near distance detection sensitivity feature with it.

Intuitively, I would have thought that the RX coil turns (inductance) would not matter at the zero point i.e 0.7 of the TX diameter. The -flux between the coils = +flux linking within the RX from a uniform thin sheet of magnetic surface.

Eric.

[Aziz]

Here is the result sheet.

Eric.

[ATTACH]22417[/ATTACH]

That's really fine and thanks for the sheet Eric.

It makes perfectly sense to use smaller RX coils now (0.33 .. 0.66). They don't work worser than mono coils regards to EMI noise induction. And the less magnetisation level of the ground will help reducing the ground response too.
Clearly a win-win situation.
Aziz

[Aziz]

All these different coil configurations are getting confusing, but the type I was referring to is separate TX and coaxial coplanar RX without any balancing, or bucking. This type can be optimised better for both TX and RX functions and gives a certain amount of near surface ground decoupling over the mono. The ground loop is the same principle but with a Large TX (1 - 10m square laid on the ground), with a small movable RX (0.25 - 1m square or round). The operator searches within the TX loop, preferably using a grid of some sort. This gives very good ground decoupling but you have to avoid getting right up to the TX, otherwise the ground signal amplitude rises sharply. Ground loops are usually used where extreme depth is required on large objects, or scaled up even further for conductive ore body location. In my view, coaxial coplanar non IB (CCNIB if you like) should be kept as a separate type from ground loop, which is offset from coaxial most of the time.

Eric.

Hi Eric,

I understand the subject now. Indeed, I didn't have a proper name for the simple TX, concentric coplanar RX PI coil and the coaxial anti-interference option of it. So I have called it simply the ground loop (GL) coil above, which isn't definitely the same of course (wrong naming). I won't call it GL now. GL coils have a larger fixed TX coil and moveable smaller RX coil and in my case, this isn't moveable and the whole coil assembly is small and moveable.

Has anyone a proper name for it? There are two options: normal and co-axial AI.

Regarding your former question:
The ground response will be reduced due to apparent (!) smaller and separate RX coil. However, we are thinking of making the smaller RX coil with more turns count (more inductivity) to get an equivalent EMI noise induction compared to the larger RX coil (the 10 inch 300 µH RX = mono PI coil as the reference). As a consequence of this, we have again more ground response near the RX coil region. BTW, we have an excellent pin-pointing and near distance detection sensitivity feature with it.

The whole coil comparison is made for an equivalent EMI noise induction (same SNR critieria). The (far) distant EMI noise source can be considered as homogenous EM field at the coil region. The EMI noise induction is directly proportional to the RX coil turns count N(RX) and is direct proportional to the RX coil flux area A(RX). The product of N(RX)*A(RX) is therefore direct proportional to the induced EMI noise too.
All coil configurations have the same N(RX)*A(RX) product (same level of EMI noise induction). ( N(RX+)*A(RX+) = N(RX-)*A(RX-) = N(RX)*A(RX) )
I'm taking the plain 300 µH mono coil as a reference coil (TX=RX). All TX coils are normalized to 300 µH (total TX inductivity = 300 µH).


I have made the following RX coil diameter relation to the TX coil diameter:
diameter(RX)/diameter(TX): 0.71, 0.5, 0.33

The smaller ones outperform even the reference coil slightly (really not significant, only 2-3%). If the coil capitance is getting critical due to higher turns count of RX, 0.5 might be a good option (outperforming the reference coil too). Or just crank up the gain, which is equivalent to increasing the turns count regards to EMI noise.
No need to make it for 0.8 relation. It doesn't do better than the smaller ones.

Cheers,
Aziz

[Ferric Toes]

Here is the result sheet.

Eric.

[Ferric Toes]

Eric, do you referring to the concentric co-planar IB coil or
the large TX, small separate RX PI coil (the ground loop coil principle)?
Please specify your question(s) more precise.
Aziz,
confused

All these different coil configurations are getting confusing, but the type I was referring to is separate TX and coaxial coplanar RX without any balancing, or bucking. This type can be optimised better for both TX and RX functions and gives a certain amount of near surface ground decoupling over the mono. The ground loop is the same principle but with a Large TX (1 - 10m square laid on the ground), with a small movable RX (0.25 - 1m square or round). The operator searches within the TX loop, preferably using a grid of some sort. This gives very good ground decoupling but you have to avoid getting right up to the TX, otherwise the ground signal amplitude rises sharply. Ground loops are usually used where extreme depth is required on large objects, or scaled up even further for conductive ore body location. In my view, coaxial coplanar non IB (CCNIB if you like) should be kept as a separate type from ground loop, which is offset from coaxial most of the time.

Eric.

[Aziz]

Aziz, back in 2002 I was interested in the ratio of TX to RX diameters to minimise the signal from surface ground viscosity response in CC coil. The computed result was between 0.7 and 0.8. Can you factor in that requirement and what is the trade off?

Eric.

Eric, do you referring to the concentric co-planar IB coil or
the large TX, small separate RX PI coil (the ground loop coil principle)?
Please specify your question(s) more precise.
Aziz,
confused

[Aziz]

Aziz, are you able to calculate the optimum position of tx between both rx coils (concentric, coplanar)? Does it make sense?

???

In case you mean the IB coil, yes. It is mandatory to compare the IB coil in an induction balanced coil condition. All IB coils are in induction balance state.

In case you mean the co-axial stacked AI IB coil (RX+, TX, RX-), the TX position is simply the mean co-axial distance of RX+ and RX-. Not required to calculate the optimum TX IB position.

In case I haven't answered your question, please specify it more precise.
Aziz

[Ferric Toes]

Aziz, back in 2002 I was interested in the ratio of TX to RX diameters to minimise the signal from surface ground viscosity response in CC coil. The computed result was between 0.7 and 0.8. Can you factor in that requirement and what is the trade off?

Eric.

[ppodg]

stupid question, removed