Digital Balanced Front End

[Anonymous]

It seems to me that complete and accurate
balancing could be accomplished in a digital
system using only two coils (Rx and Tx) without
loosing any sensitivity. The third coil is
effectively simulated by storing the sampled Rx
signal with no target (setup mode) as a reference
and subsequently subtracting it from the Rx
signal prior to fourier analysis in search mode.
Drift could also be detected and the reference
could be adjusted as necessary at a slow rate
to compensate.
As a guide, a 20Mhz 68000 CPU can do a 16 bit
1000 point fourier Conversion in about 100mS.
Cheers
Malcolm

 

[Anonymous]

Try a TMS 320VC5510 DSP, it can do the same in just over 5mS.
68000 just plain SUCK for detectors, they're TOO slow, and drain batteries like nobodies business.
BTW, your idea is correct, this system DOES work.
Sorry I cant tell you any more, and I'd advise anyone else to forget trying it commercially, as there is a patent pending on this, and the holders are NOT very friendly!!
Sorry Malcolm.

 

[Anonymous]

Sean:
Without knowing for sure what's actually being disclosed and claimed in the patent app, it's not possible to say for sure, but......
sounds like it fails the test of obviousness in light of abundant prior art.
--Dave J.

 

[Anonymous]

Hi Dave,
Yes true, but what is obvious now, was obscure yesterday, otherwise all things would have been invented long ago.
REMEMBER, the simplest ideas are the best. and if you want to see just how easily a patent can be obtained for an item, try looking at any of the Japanese patents for metal detectors.
They're ALL COMPLETELY USELESS, and so obvious, that they were probably dismissed by many others.
As to prior art, I agree, but if White's can get a patent on one item, then Garrett on practically the same withing 6 months, then why bother with referencing prior art at all?
Any how, I believe this company was using this system quite some time ago, and has only now decided (why?) to patent the idea, or at least try. Perhaps what is being disclosed on this forum by the many clever people who frequent it has got them worried!