VLF with direct sampling

[pepe]

Hi

I am writing here first time so hello everyone . I'm from Poland so sorry for my english.
I'm thinking of building a metal detector with direct sampling. Signal from rx coli will be sampled direct with precision fast ADC and all calculation will be done in processor.
All circuits that I know use synchronous rectifiers to split signal on two components - magnetic and electric (or more if used more freqency ex. Whites V3i). My previous prototype also use synchronous rectifiers (link for prototype's movie: http://youtu.be/5OF-lGxCKCo )
Do you know someone VLF metal detector with the direct tx signal sampling?

B.R.
pepe

[Carl-NC]

The Minelab X-Terras use direct sampling, and the White's 6T uses quadrature direct sampling. I don't know of any canned projects that do.

[pepe]

I would like to use the sampling frequency of about 1MHz - 2MHz. The transmitter would be built from the H-bridge in order to achieve high current in the coil transmission with acceptable power consumption from the battery (return energy to the capacitor).
I built this type of detector but he only used the 12-bit ADC - range was woeful.
Now I plan to use the 24bit converter.
I wish I had found someone who has already tried to do so.
Minelab probably will not tell both details.

B. R.
pepe

[Skippy]

The direct sampling (24 bit ADC) Minelab Xterra circuit is available here:
http://phazitron.narod.ru/repair/xterra.htm.

[pepe]

Thanks for Xterra circuit It has very simply rx and tx and audio stage - all build from audio codec. It is very smart

[kt315]

with direct sampling are projects:
Tango - http://www.md4u.ru/viewforum.php?f=2...2c9e120358ca70
Quazar - http://www.md4u.ru/viewforum.php?f=9...c91ffbd841e0ef

good luck

[pepe]

Fine projects . In my design I plan use much more powerfull CPU (arm - stm32f4) an faster ADC. For display I will use second cpu (one box with metal detector and one with display to have better balance).

B.R.
pepe