What is the relationship of uH and sensitivity?

[Carl-NC]

"His detector was not that much better then mine, yet he was finding things that I was missing."

If you are using a Sharper Image metal detector, then you are close to the bottom of the barrel, and it's likely his detector really was much better than yours. You will come out way ahead if you keep the coil and replace the detector, than if you keep the detector and replace the coil. Since your detector already paid for itself, I recommend you get a new detector paying for itself.

For a sinusoidal voltage driven TX coil, the magnetic field is inversely proportional to the number of turns, or the square-root of inductance. Pulsed coils can be different depending on the drive circuitry.

- Carl

[WM6]

I had same machine with same coil data, named "Black Knight".

The same model currently selling in EU as "Klarstein" (seller from Berlin) Silver Edition 71.90EUR.

http://cgi.ebay.fr/KLARSTEIN-DETECTE...item3cbbf72b80

[ivconic]

Yes I did mean mH. Thanks for the correction.

Seems that is "same old" machine, packed in several different packages, which usually came from different manufacturers from China.
Complete chaos there in their market! God only knows who is copying whom there!?
I had same machine with same coil data, named "Black Knight".
It is descent as start up.
I was satisfied with it's stability and Disc on mineralized soils.
Yet i was not satisfied with depths.
Coil data and some stages in machine mostly reminds me on Fisher...
So it would be good advice you to try it with some original Fisher coil.
Closest would be coil for Fisher's 1265, 1266, 1236.....
Pick one and try...
Or... DIY coil for SMW, explained somewhere on forum. Search it.

[WM6]

So I have decided to build a different coil for my detector. Yes, I know I could just buy a better coil, but I would rather have fun building one.

It is hard to buy different coils for Chinese detectors even if you wish only to replace stock one.

Detector you have is one of the better Chinese detector in its class.

It make sense to build better coil, say DD one.

Wish you all success with DIY.

[Beach]

For a given coil diameter, supply voltage, and transmit frequency (assumes sinusoid), a lower inductance increases the transmit field strength.

OK, now I am all confused....

I have done some experimenting with magneticlly levetated pulse motors and have found the bigger coils i used (meaning more copper and turns) the faster my motors went. The asumpting being that the more copper I used the higher the inductance therefore the higher the inductance the more powerful the coil....

So how can a lower inductance increase field strength? I am getting something wrong here....What am I missing?

Thanks!

[Beach]

Did you mean to write mH?
I don't know of any detector that uses (or can use) a TX coil of only 2.1uH.

Yes I did mean mH. Thanks for the correction.

[Beach]

Hi, if you would ever open it, could You post some photos from inside?
I am not sure if You get right Your uH numbers - it is a litle unusual.
Have a good fun.
Regards,

I am afraid to open it because I might break it. Also I ment mH not uH.

[Beach]

Maybe this one

They might be the same ones, but mine looks a bit different...

[Qiaozhi]

The readings on the coil are Tx 2.1 uH at 7Ω. Rx 96 uH at 27Ω.

Did you mean to write mH?
I don't know of any detector that uses (or can use) a TX coil of only 2.1uH.

[6666]

Maybe this one

[wam]

Hi, if you would ever open it, could You post some photos from inside?
I am not sure if You get right Your uH numbers - it is a litle unusual.
Have a good fun.
Regards,

[Beach]

What detector are you using?

It is a sharper Image express. The down side is that it is cheep, the up side is that it paid for itself in 5 months this summer.

The readings on the coil are Tx 2.1 uH at 7Ω. Rx 96 uH at 27Ω.

[Beach]

For a given coil diameter, supply voltage, and transmit frequency (assumes sinusoid), a lower inductance increases the transmit field strength.

OK, let me see if I can rap my beedie little mind around this....

If my stock transmit coil reads 100 uH and I wind one that is 90 uH, I can gain 10 percent more field strength?

[Carl-NC]

For a given coil diameter, supply voltage, and transmit frequency (assumes sinusoid), a lower inductance increases the transmit field strength.

[kasparov747]

what is a lower L

Carl when you say a lower L on the transmit coil will help depth will more battery usage, what is meant by a lower L? Thank you for your time.