Measuring PHASE SHIFT IN PI

[Tinkerer]

During many experiments doing ON TIME sampling, I have found that there is some kind of "PIVOT" in the response.
It is like there was an "INVISIBLE SINE WAVE" in the response from the target.
The "PIVOT" would be the point 0 where the "relative polarity" changes.

I believe that with the right signal processing we should be able to read the phase shift in this sine wave, caused by the different metals, just as it is done with VLF.

I SAY PI TARGET DISCRIMINATION IS POSSIBLE

I am starting this new thread inviting everybody who believes that it is not possible to do target discrimination with PI, to discuss the subject with others who believe it is possible.

Tinkerer

[aft_72005]

I SAY PI TARGET DISCRIMINATION IS POSSIBLE

Yes , pi detector be able working at discrimination mode .
I did it .
Best regards.

[Esteban]

Circuit that detects time positions of peaks and valleys in the input-voltage waveform.

http://www.edn.com/contents/images/6442431.pdf

[Tinkerer]

Yes , pi detector be able working at discrimination mode .
I did it .
Best regards.

Would you mind telling us how you do it?

Tinkerer

[Qiaozhi]

During many experiments doing ON TIME sampling, I have found that there is some kind of "PIVOT" in the response.
It is like there was an "INVISIBLE SINE WAVE" in the response from the target.
The "PIVOT" would be the point 0 where the "relative polarity" changes.

I believe that with the right signal processing we should be able to read the phase shift in this sine wave, caused by the different metals, just as it is done with VLF.

I SAY PI TARGET DISCRIMINATION IS POSSIBLE

I am starting this new thread inviting everybody who believes that it is not possible to do target discrimination with PI, to discuss the subject with others who believe it is possible.

Tinkerer

Hi Tinkerer,

What sort of effect does the balance between the coils have on the target response during the ON period? I would imagine that this adjustment is quite critical.

[Qiaozhi]

Yes , pi detector be able working at discrimination mode .
I did it .
Best regards.

Would you mind telling us how you do it?

Tinkerer

And how successful is the discrimination when compared to a VLF-IB?

[Max]

And how successful is the discrimination when compared to a VLF-IB?

that's the point: any serious attempt of implementing disc in a PI design must face that any VLF-IB design is fairly superior to that: facts.

I think most people here belive a true fault free discrimination in PI is possible... though till now not demonstrated by any commercial product.

It's like with eco-cars.... you'll put inside the hydrogen... oh yeah...
But how the hell that hydrogen is produced ??? By some nuclear reactor generated current , eh ???

Then add to the "clean" hydrogen the costs (not only money) for a nuclear plant here and there and you'll see that probably the cleanest REAL USABLE car around is fueled by elephant $hit made METHANE!

Same apply to PI... someone will make the people think they can get everything easy... power (depth) and accurancy (discrimination) and it isn't. It's never so simple in real world.

Kind regards,
Max

[Qiaozhi]

that's the point: any serious attempt of implementing disc in a PI design must face that any VLF-IB design is fairly superior to that: facts.

Maybe Tinkerer will have more success.

[Tinkerer]

Circuit that detects time positions of peaks and valleys in the input-voltage waveform.

http://www.edn.com/contents/images/6442431.pdf

Esteban,

thanks for the feedback.
I will post some pictures of the PIVOT to illustrate what I am talking about.

Tinkerer

[Tinkerer]

Hi Tinkerer,

What sort of effect does the balance between the coils have on the target response during the ON period? I would imagine that this adjustment is quite critical.

Hi Qiaozhi,
The balance of the coil is indeed the critical point.

It took me years to find ways to adjust the balance of the coil after it is cast.
I have now 3 different ways to make adjustments, all of which can be done by pots or digital potentiometers controlled by the MCU.

Tinkerer

[Tinkerer]

And how successful is the discrimination when compared to a VLF-IB?

I really don't know yet. We will have to find out.
I am hoping that the discrimination capabilities will be very similar to VLF.

Tinkerer

[Tinkerer]

Hi Max,

OK we will make a special environmentally friendly model for you.
We take this picture of the elephant, roll it up and stick it into coil.
Then we zap it with 66A current to generate a 666 Gauss B field intensity.
This should beat enough C_R_A_P out of the elephant to generate rainbow colored eddy currents.

Tinkerer

[aft_72005]

And how successful is the discrimination when compared to a VLF-IB?

Hi Qiaozhi
I design and built discrimination pi detector approximately seven years ago.
It had capability discriminate between Ferro and nonferrous metals.
If pi discrimination compare with vlf detectors , it was weaker than VLF .
Best regards.

[aft_72005]

Circuit that detects time positions of peaks and valleys in the input-voltage waveform.

http://www.edn.com/contents/images/6442431.pdf

Hi Esteban
It is notable .
Best regards.

[Qiaozhi]

Hi Qiaozhi
I design and built discrimination pi detector approximately seven years ago.
It had capability discriminate between Ferro and nonferrous metals.
If pi discrimination compare with vlf detectors , it was weaker than VLF .
Best regards.

That is very interesting.
As most serious detectorists discover, it is the ferrous versus non-ferrous discrimination that is important. Discrimination between various non-ferrous targets can be useful in certain circumstances, but often it is not much more than a guess. That's why commercial detectors, that display the likely target type, are calibrated for coins, as these tend to be more consistent. The main problem with PIs being used inland is their love of iron, and (unless you're a relic hunter) this is usually what you want to avoid.

Are you willing to publish the details here?