Theories about coil-shielding

[kt315]

Is your shield conductive?

ok. i see you are very active in the field of the shielding matter. give me a link on your album with pics of the shielding.
then i will give mine link in exchange. i must see your awesome level.

[kt315]

Is your shield conductive?

what (WHAT) relation HAS the shield conductivity to the protection from ESFI? i see you are not able to read my simplest questions.

[Hyena]

ok. i see you are very active in the field of the shielding matter. give me a link on your album with pics of the shielding.
then i will give mine link in exchange. i must see your awesome level.

I do not see answer to my question. Your access is very authoritative and I do not like it.

You just changing topic and do not want to admit, that eddy current is in every... I will not write it again. But what I wanted to say is fact, that it will be there no matter if it somehow affect detection or not. So you are using word nonsense wrong.

I am shielding with graphite, aluminium foil and copper self adhesive tape. I do not have album, but if you wish, I will make it for you.

Without conductivity your shield will not work as shield against electrostatic.

[kt315]

Without conductivity your shield will not work as shield against electrostatic.
----
again nonsence from your side. I LEAVE YOU HERE GUYS WITH YOUR NONUNDESTANDING just i do not want to waste my time on teaching of you.

[makaras]

My first post here..

Aluminum foil and graphite are perfect material but copper self adhesive tape is never tested..

[WM6]

Without conductivity your shield will not work as shield against electrostatic.

Correct.

We should add only, that to avoid some interferences in coil working,
those shield conductivity should be proper set (set to minimize eddy
currents and still retain enough conductivity to promptly maintain
changeable electrostatic charges between shield and soil).

Important especially in PI design with very early sampling.

So it is about proper conductivity (or resistance) of coil shielding.

[Altair]

Correct.

We should add only, that to avoid some interferences in coil working,
those shield conductivity should be proper set (set to minimize eddy
currents and still retain enough conductivity to promptly maintain
changeable electrostatic charges between shield and soil).

Important especially in PI design with very early sampling.

So it is about proper conductivity (or resistance) of coil shielding.

[Altair]

Altair please be careful how you converse with other respected members (Kt315 is a very old and respected member of our community) people here are a wealth of information and experience and whatever your own background may be (you are relatively new member) please display grace and tolerance to all...... you never know there may be some people here with PHD's and/or 40 odd years experience in the field.....
Best wishes

If you have others advice for me on this matter, please, send me a PM, thank; this is a technical forum.

To close, I think that anybody is reading the thread with a normal critical judgment capacity, will be able to draw their own conclusions.

[Koala]

In a VLF coil the shielding makes or breaks it.

Manufactures even struggle to get a reliable system.

Marko Racer had a batch that couldn't run at very high sensitivity

As did a batch of Garrett Ace 250

Why do manufactures use graphite when is not easy to connect to instead of aluminium which you can crimp to or copper you can solder to ??

Tesoro went one further as on some of their coils the shell is also conductive


Having wasted time and money building coils that don't work at 100% I will stick to what works in the real fields

[makaras]

Thats right. Material should be Hard and brittle but during bonding time, it should not de-shape the coil otherwise it would destroy the nulling. Slow setting epoxy resign with smallest grain sand or some powder glass should do the work.

[Carl-NC]

Some thoughts on this topic...

High-R shielding works well in some designs, not in others. The TDI requires 6 coats of graphite paint to get the shield R low enough to be effective. Eric has commonly used lead tape in his PI designs.

Graphite paint is commonly used in mass production for cost purposes. It can be difficult to control, but generally not difficult to connect to. Embedded wire or conductive tape work fine. Experienced manufacturers know how to do all this well.

In VLF, shielding can affect the loop null depending on geometries. It is usually predictable and in production the loop is slightly mis-nulled before the loop bottom is applied. Or, in the case of the e.g. Fisher F75 loop, final-nulling is done in a little access door after the bottom is applied.

Low-R shielding can alter the PI decay, again, depending on geometries, but it tends to be a static effect. I've applied aluminum foil directly to a bundle of magnet wire with little effect at 15us. If you are trying to achieve super speed, then some gap and close attention to symmetry are important.


Footnote:
KT, please don't provoke people with denigration or demands for credentials. If you have a question, ask the question. If you disagree, state your reasons.

[kt315]

Carl

if in shield there are Eddy currents (they claim that) that means a part of TX energy is lost. am i right or no?

[kt315]

ok Carl. you are silent. if i see good and right answer i never comment after. one cause - no reason to comment where is the good comment.
if the people are in prostration it is their only problem. i left this thread. let people to be in the darkness of deeply delussion. their Holy right.

[Andi68]

Breathe long and deep

[Carl-NC]

Carl

if in shield there are Eddy currents (they claim that) that means a part of TX energy is lost. am i right or no?

Correct, and you want to minimize that. Ideally the shield should be perpendicular to the flux so that the cos(Θ) in Faraday's Law is 0. But there will be small losses, and this is evident with VLF coils when the graphite-coated bottom is applied and the null shifts. It is evident in PI coils when the decay curve shifts.