An impossible and insane thought ???

[Aziz]

Even if the "rule of 64" does not apply for distances less than the coil radius / diameter, how is that of any benefit if you can already detect a target at a distance beyond the coil diameter?

See post
http://www.geotech1.com/forums/showt...731#post117731

coil diameter = 2 * coil radius = 2*R
(see 2R to 4R -> factor 39.3 and not 64!)

Aziz

[Davor]

Eddy current dampened oscillator. Metal in the field of the coil absorbs energy, reducing the amplitude of oscillation.

--Dave J.

I expected something more exotic. Thanks.

[Qiaozhi]

See post
http://www.geotech1.com/forums/showthread.php?17063-Oscillator-power!!!!&p=117731#post117731

coil diameter = 2 * coil radius = 2*R
(see 2R to 4R -> factor 39.3 and not 64!)

Aziz

That doesn't really answer the question.
If you can already detect the target at a distance beyond the coil diameter, then how will increasing the power help when the target is now close to the coil? All you will achieve is an increase in ground noise. It would be like standing a bit closer to Carl's locomotive.

[Aziz]

That doesn't really answer the question.
If you can already detect the target at a distance beyond the coil diameter, then how will increasing the power help when the target is now close to the coil? All you will achieve is an increase in ground noise. It would be like standing a bit closer to Carl's locomotive.

A good example.

The power increase makes sense, when you increase the coil size. So getting factors below 64.
You also could increase the SNR (increase the signal, decrease the noise).
You could increase the TX size (decreasing the power factor) and use smaller RX coil size (decrease the induced noise).

But the 64 power rule is a myth. Ground loop principles won't work otherwise.
Aziz

[Aziz]

Who made the "Top-Hat" IB AI coil?
Large TX, small RX (1/3 - 1/2 diameter of TX).


BTW, this is almost a ground loop principle!!!
Aziz

[Pennypacker]

But the 64 power rule is a myth. Ground loop principles won't work otherwise.
Aziz

I fail to see the connection here, could you explain? Thanks.

[Aziz]

I fail to see the connection here, could you explain? Thanks.

Oh man!, since my IQ went almost to negative infinite (thanx to UFox making this possible), I can't do the math proof anymore.
I'm not that smart as Rafferty, Ufox or BC.
*LOL*

Sorry, you have to look for the convenient threads in this forum or other forums. I don't have the piece of paper work anymore (the math proof on paper). I would require many many colored pills to take the challange once again.

Cheers,
Aziz

[Qiaozhi]

A good example.

The power increase makes sense, when you increase the coil size. So getting factors below 64.
You also could increase the SNR (increase the signal, decrease the noise).
You could increase the TX size (decreasing the power factor) and use smaller RX coil size (decrease the induced noise).

But the 64 power rule is a myth. Ground loop principles won't work otherwise.
Aziz

That still doesn't make any sense.

How can you increase the depth close to the coil by increasing the transmitted field strength when the target detection is already beyond the coil diameter distance?
Or are you implying that this is only true for exceptionally small targets in conjunction with large coils? Surely the response from other larger targets will dominate, not to mention the ground response.

[Pennypacker]

You can't just sum it up for me? lol

OK I read your thread linked above.

You are essentially saying we can ignore the "rule of 64" if we are closer than infinity because the response is logarithmic rather then linear. However with the response being logarithmic, the added Tx power would still be significant?
So you guys basically agree with each other?

[Aziz]

That still doesn't make any sense.

How can you increase the depth by increasing the power when the target detection is already beyond the coil diameter distance?
Or are you implying that this is only true for exceptionally small targets in conjunction with large coils? Surely the response from other larger targets will dominate, not to mention the ground response.

Hi George,

my numerical electro-magnetic simulations indicate (the Biot-Savart and Maxwell equations thing), that it isn't dependent on the target size. But you have fairly missed to make the math proof and I didn't provide you the proof. My bad. Sorry for this.

Of course, you will get more ground response with more TX power.
And you will get more EMI noise with larger coils.

But the fact still remains: The 64 power rule is a MYTH!!!

Who dares to make the real proof?
I have to take more blue pills to be able to do this.
Blue pills? (Viagra? Tavor? I don't know anymore. )

Aziz

[Aziz]

You can't just sum it up for me? lol

OK I read your thread linked above.

You are essentially saying we can ignore the "rule of 64" if we are closer than infinity because the response is logarithmic rather then linear. However with the response being logarithmic, the added Tx power would still be significant?
So you guys basically agree with each other?

Trust in my calculations. I'm a math genius, when I take more blue pills. *LOL*
Aziz

[mikebg]

What limits the sensitivity of a metal detector?
Why nobody speaks for "signal-to-noise ratio"?

http://en.wikipedia.org/wiki/Signal-to-noise_ratio

I know why. Because nobody is ham radio designer. Since I'm a "theorist", I speak myself .

[Pennypacker]

Ya ya ya, we get it, you like HAM radios.

EDIT: Perhaps I was a little harsh, care to expand with use of an example? Are you saying this is the limiting barrier in today's designs?

[Davor]

2box designs seem to defy the 64x rule by means of improved S/N.

[Carl-NC]

What limits the sensitivity of a metal detector?
Why nobody speaks for "signal-to-noise ratio"?

I think everyone looks at SNR. Intensely.