GPX Audio Question (Limited English).

There is no need to mix each channel as the signals are mono - they are split in the GPX battery audio circuitry to form a "stereo" signal.

Using the oscilloscope you will not be able to tell the difference between metals ( I have done this many, many times lol). Being a PI machine, the audio output does not have differing signals for metal types. The audio is generated by a VCO. The voltages used to drive the VCO do not vary due to metal type. In basic terms a PI machine is a time based circuit. Hard to describe without going into full detail on how a PI machine works.

ya zhdal vash otvet, uvazhayemyy steelPHASE! Vasha kompetentnost' ne vyzyvayet somneniy. YA zakazal vash sP01 na Ebay i ochen' nadeyus' yego poluchit'. No, yest' mneniye, chto sub'yektivno signaly chernogo metalla i tsvetnogo razlichayutsya ukhom i khochetsya uvidet' nekoye prisposobleniye. YA ispol'zuyu VLF Tekhnetiks G2+ dlya identifikatsii, k sozhaleniyu,na malom rastoyanii.
I was waiting for your reply, dear steelPHASE! Your competence is beyond doubt. I ordered your sP01 on ebay and really hope to receive it. But, there is an opinion that, subjectively, the signals of ferrous metal and non-ferrous differ by the ear and I want to see some kind of device. I use VLF Technetics G2 + to identify, unfortunately, at a short distance.

Decoy said:

you would probably be better of with an audio spectrum analyser, that is assuming the detector outputs different audio frequencies corresponding to what it has detected and not just amplitude of the same frequency.

Click to expand...

Unfortunately the GPX does not put out different frequencies to indicate different materials.

It uses a VCO to generate audio. The voltage supplied to the oscillator varies depending on the depth/size/and to a small degree, composition. The issue is that a small round bit of gold will sound like a small piece of lead. A shallow screamer of a nugget will sound like a shallow ferrous target. Porous, reefy gold can sound like bits of brass or thin wire.

With a PI detector there is NO way of accurately differentiating targets. The first manufacturer able to achieve this will make a fortune.

One word.
discrimination.

The holy grail for a PI detector if some one comes up with it.

Tathradj said:

One word.
discrimination.

The holy grail for a PI detector if some one comes up with it.

Click to expand...

Minelab PI's do have an iron reject function Tathradj.
It's about as efficient as the discrimination setting on a VLF but i rarely use it and dig everything.
If we don't use it we tend to forget it's there. :Y:

steelPHASE said:

Decoy said:

you would probably be better of with an audio spectrum analyser, that is assuming the detector outputs different audio frequencies corresponding to what it has detected and not just amplitude of the same frequency.

Click to expand...

Unfortunately the GPX does not put out different frequencies to indicate different materials.

It uses a VCO to generate audio. The voltage supplied to the oscillator varies depending on the depth/size/and to a small degree, composition. The issue is that a small round bit of gold will sound like a small piece of lead. A shallow screamer of a nugget will sound like a shallow ferrous target. Porous, reefy gold can sound like bits of brass or thin wire.

With a PI detector there is NO way of accurately differentiating targets. The first manufacturer able to achieve this will make a fortune.

Click to expand...

I would not trust a VLF to differentiate any alloy from a piece of gold either mate.
I would have to dig it up... :|

said:

Grandfather Driver! More. Any information that may seem secondary to you can be extremely important to me.

Click to expand...

Irony. I had not known that DED is 'Granddfather' in Russian!

jumping back to CP's post #22 he mentions that he uses VLF Technetics G2
It is an interesting thought on what might be possible!
I have seen the pulse waveforms from a GPX by Woody Detectormods on YouTube, but have never seen the output of a VLF on a scope.

Ded Driver said:

jumping back to CP's post #22 he mentions that he uses VLF Technetics G2
It is an interesting thought on what might be possible!
I have seen the pulse waveforms from a GPX by Woody Detectormods on YouTube, but have never seen the output of a VLF on a scope.

Click to expand...

The title of the post is about a GPX so I assume he also has a VLF machine as well as the GPX. VLF machines already have discrimination and the audio coming out is post processing and often has already been processed to indicate target composition.

The pulse waveforms Woody shows are not whats coming out of the detector. They are what is going into the coil. In a VLF its basically just a sine wave going into the coil.

A great book thaat goes into some depth on detectors and how they work is called "inside the metal Detector" and is written by Carl Moreland from over on the Geotech forum (he used to work for Whites and now is with First Texas).

regards
Pat

Merry Christmas to all !!! Yes, indeed, I have a GPX-4800, Technetics G2 +, NF 15 coils, 19 mono and Somander 18DD. I find a target with GPX, (Technetics cant hear it), dig and then with Technetics, (on the VDI scale, electrical conductivity) I make a digit output until I dig 40, I dig from 50 and above. It saves me time and energ

Not a bad concept CP. I don't dig everything either, (I know I should, but I don't.) If i had a digital read out it would make my life easier also. Problem is what if your reading of 40 is a deep piece of gold? There's only one way to truly find out. Pick and sweat

Not. I dig only that above 40 on Technics. Many do not dig everything in a row, based on subjective sensations. If this subjectivity exists, then you can try to justify it instrumentally, even if its 50 to 50.