Dual Technology Detector (VLF/PI)?

[goldjackal]

I had already posted this question, I thought, but apparently it didn't post properly.

Is there any particular reason why a single machine using both PI and VLF technolgies couldn't be built?

I've done a lot of research and studying on VLF, and know the basics of PI, but maybe I'm missing something. Is there something inherent to the coil design that prevents the use of both technologies on one machine?

Now obviously I'm not talking about using them both at once, but why couldn't I run a machine in PI mode, and when I find something, then change over to VLF? Or something along those lines.

I look forward to any replies.

Thanks,

- Jack

[ivconic]

Sascho's Pulse IB is another approach..

[Max]

I had already posted this question, I thought, but apparently it didn't post properly.

Is there any particular reason why a single machine using both PI and VLF technolgies couldn't be built?

I've done a lot of research and studying on VLF, and know the basics of PI, but maybe I'm missing something. Is there something inherent to the coil design that prevents the use of both technologies on one machine?

Now obviously I'm not talking about using them both at once, but why couldn't I run a machine in PI mode, and when I find something, then change over to VLF? Or something along those lines.

I look forward to any replies.

Thanks,

- Jack

Hi Jack,
good question... hybrid detector was an argument before and before... the big problem is about coil.

If you wanna made a coil that's good for both PI and VLF you have the energy storage problem that is really important for PI sensitivity ... the more the storage... the more the time you have to wait till you can sample... so , at the end, a higher energy storage means that you cannot sample at 10-15uS that's the delay interval for max sens e.g. to small gold items.

Energy stored is E= 1/2L*i^2

so you have to reduce L cause if you reduce i you reduce the magnetic field.

That's why most small PI coils are around or under 300uH inductance.

The VLFs are about good tollerant about inductance on the TX side... you can modify inductance to match e.g. a particular frequency for TX side but generally speaking they aren't so tollerant on the RX side... cause of phase problems.

So the question is: can you build a TX coil that match both PI and VLF requirements ? The answer is yes in a large amount of cases... but you need choose something better than e.g. a Colpitts osc to drive TX in the VLF... and , of course, you cannot operate PI during VLF operations and the reverse... cause you can use the coil just for one purpose at a time (frequency or time domain).

The Sasho's approach is different, as Ivconic stated, cause he play with pulsed TX output and about a traditional VLF disc system... so you have more power on TX but RX is treated like in other VLFs. That way you can gain depth like in PIs, with stronger field (what I call "brute force approach"), but you'll take also some problems like PIs have... I'm thinking at e.g. hot rocks detection, pottery, fired-clay etc maybe you know already.

Think about before putting e.g. 100Vpp on coil

Best regards,
Max

[sharky]

I had already posted this question, I thought, but apparently it didn't post properly.

Is there any particular reason why a single machine using both PI and VLF technolgies couldn't be built?

I've done a lot of research and studying on VLF, and know the basics of PI, but maybe I'm missing something. Is there something inherent to the coil design that prevents the use of both technologies on one machine?

Now obviously I'm not talking about using them both at once, but why couldn't I run a machine in PI mode, and when I find something, then change over to VLF? Or something along those lines.

I look forward to any replies.

Thanks,

- Jack

U can use both but to drive the coil u need an DAC driven from a micro, DAC output is sinewave (u can even change te wave shape, even stop after few pulses) which drives the mosfet in low power. For PI the thing is obvious, both PI and VLF use dual coils. fet in VLF/Induction works in continuos mode ie input is sinewave...blah blah blah

[willy]

Dave Emery's Pulse devil is, as far as I can tell, a PI/IB hybrid. He's talking about 'maybe' having it for sale around Christmas. ..Willy.

[Geo]

I think that you can make it by using a DD coil. PI and VLF will have the same Tx transistor (will change the input frequency or pulses) and the Rx coil will connecting to vlf or to Pi receiver. Maybe you will not take the full power but i think that it will work good.
My DP coil has an inductance of 1mh so we can use it for vlf.
But for me at the most cases the VLF is better to PI if i use a normal disc coil. If the ground is very heavy then the PI is better and the VLF is very bad. So for me it is better to use a VLF detector for all the normal cases and a PI for the heavy ground, not one for both cases.

[DJ_AM777]

Dual technology MD VLF/PI

HI,THERE IS AN APPROACH A MD WITH DUAL TEC (PI & VLF) FROM ELEKTOR MAGAZINE . I HAS IT BUT IN PERSIAN LANGUAGE.