Let's made a PC-base metal detector with usb interface !!!

[Aziz]

I am back again.

Hi,



sadly, the arrest warrants did not come to execution. They know now, what I was going to do. True justice has won once more. I still expect further trouble but I am prepared now. They have played their big joker and have finally lost.

Let's focus to our business now.

Aziz

[Aziz]

Coil Analysis

Hi all,

as I have packed all my project stuff and brought them to my parents due to latest project actions (Jail-project) and additionally beeing totally bankrupt at the moment, I will focus to coil analysis section. You will love it. My coil analyzing software is capable for such tasks. If not, I'll make it possible.

I will analyse different coil configurations and compare them together. The criteria for the comparison will be the same condition (target, current, frequency, wire type, inductivity and total coil size). I will discuss furthermore how the disadvantages of a coil configuration can be compensated and what further effects will have on it.

This is an interesting task for a while. So give me some time to start with.

Cheers,
Aziz

[WM6]

Hi all,


This is an interesting task for a while. So give me some time to start with.

Cheers,
Aziz

Hi Aziz

we all are with you and support your great work. Avaiting for further coil analysing!

Krauts can put in jail only body but not a soul.

Best wishess to you!

[Aziz]

Preparation for Coil Analysis

Hi all,

I will analyse mono loop round coil, induction balanced coils (DD and concentric co-planar), figure-8 coil (anti-interference coil), and maybe the two-box coil too. The latter two types are quite difficult to manage as the max. sensitive position is not on the center of the coil configuration.

Let's take a total coil size of 10 inch diameter (round, 254 mm diameter). Single coils will have an inductivity of 300 µH (TX=RX=300 µH). Seperate TX/RX coils should have each 300 µH coil (TX=300 µH, RX=300 µH). Compound TX coil should have total 300 µH. DD coil size will be the same total size of the mono loop coil.

Transmitter coils (TX) will be displayed red. Receiver coils (RX) green. Both TX, RX wire will be 1 mm diameter round copper wire (as simplified coil model). Target (20 mm diameter, 1 mm diameter single loop wire coil) yellow (gold conductor).

The target will be placed on it's sensitive hot spot axis of the coil configuration and will be swept from 1 inch to 30 inch distance (height) (1 inch step size). The target response voltage seen by the receive coil will be calculated and all the coils will be compared together later. If there is no real receive coil, than the transmitter coil is acting as a receive coil.

The transmitter coil will be excited by a 1 A coil current at 1 MHz. I am using the 1 MHz high frequency excitation just to increase the very low voltage levels to have some more accuracy. Otherwise, I would have lot's of zeros in my numbers. Skin effect is not taken into account (not to worry about the 1 MHz). All coil models are just simplified wire models (less work and fast). For our purpose, the simplified models are accurate enough for a proper comparison of the coils (Biot-Savart model).

Below is just a scheme of a mono loop round coil with some infos. I will put the scheme of the coil and the calculated target response voltage together.

Let's start.
Aziz

[Aziz]

Hi all,

who is going to invest for two new coil patent applications (50:50, your money, my ideas)? Just kidding. I am not interested.

But I have found some very very interesting coil configurations. I'll investigate it further.

The figure-8 coil and the two-box coil are causing too much work (due to non-linear high sensitive position). They aren't the huge work worth. I'll drop the analysis.
I'll take some more time to present the results. Stay tuned..

Cheers,

Aziz

[silverdog]

I notice Garraett are claiming improved performance from their blunted tip DD coil on the new Euro Ace
http://www.garrett.com/euroace/page2.htm

[Aziz]

Hi Silverdog,

I haven't checked it yet, whether there is a real significant advantage. But all induction balanced coil types are very sensitive to hot ground mineralization. Only a good ground balance will solve the problems.

--------------------------------------------------

I have a very interesting and novel anti-interference coil, which goes deep (!!!) and has a SNR increase of 10-20 dB. This coil should be very quiet.
Could be a real ripper coil. But I haven't investigated and compared it to other anti-interference coil types yet.

Aziz

[Aziz]

Breakthrough in Anti-Interference Coil Design

Yep, it's real. The potential investors business ratio has been radically changed into 10:90 (me 90% ). It seems, that all the coding effort of my coil software will pay itself off now.

I won't reveal the details of the novel invention. Who is gonna hire me now?

Aziz

[Aziz]

Hi all,

after making the calculations for the mono coil, I had a brilliant idea. This lead to the new coil design. I will start making the other coil types (DD, concentric co-planar) tomorrow and hope to get finished the comparison. Unfortunately, DD and concentric co-planar coils must be precisely induction balanced, which cause a lot of work. So forgive me, if I can't show the results tomorrow.

Cheers,
Aziz

[Aziz]

Coil Schemes

Below are the coil schemes of three different coil types:
- Round Mono Coil
- Round Double-D (DD) Induction Balanced Coil
- Round Concentric Co-planar Induction Balanced Coil (inner diameter 5 inch)

[Aziz]

Coil Comparison Results

Below are the results of the coil comparison:
- Calculated values
- Comparison chart (log-view)

Discussion will follow..

[WM6]

Hi Aziz,

mono sems not so bad.

What exactly mean Target Heigt? Distance between target and coil (coil above target)?

Can you calculate different type of wire (Cu, Al) and shielding too?

Hov do you supply this coils? By sinus? By rectangular? By pulse?

[Aziz]

Hi Aziz,

mono sems not so bad.

What exactly mean Target Heigt? Distance between target and coil (coil above target)?

Yep, that's right. Similar to air-test configuration. Just elevate the target above the coil and measure (calculate) the target response only seen by the receive coil. Self induction/IB mismatch of the TX coil into the RX coil is not taken into account (not relevant for target response only).

[Aziz]

Hi Aziz,

mono sems not so bad.

What exactly mean Target Heigt? Distance between target and coil (coil above target)?

Can you calculate different type of wire (Cu, Al) and shielding too?

Hov do you supply this coils? By sinus? By rectangular? By pulse?

I see, you have put more questions.

Yes, I can use different type of conductors. But they haven't relevance for the coil current as I am using a current source drive (1 A at 1 Mhz). Shielding effects were not taken into account (this is a highly non-trivial job man, I am using only simplified models).

My simulation software uses sine-wave currents (easy calculation). The first derivation of it is used for the induction calculations and the maximum value is taken. So effectively max. dI/dt is taken for target response calculations. For our comparison, this is irrelevant. The performance of the coils apply to other current wave forms too.

Note, that the comparison is made under same conditions: same inductivity (300 µH), same coil current, same frequency, same target, same coil case diameter (10 inch), etc.

[WM6]

But they haven't relevance for the coil current as I am using a current source drive (1 A at 1 Mhz).

.

Why do you use 1MHz instead of say 10kHz?

Eddy currents are not the same at 1MHz as at 10kHz, and skin effect can be observed at higher freqency too.