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Originally posted by deemon
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Of course , I can copy it here ... the only problem is this fantastic captcha on AEGPF forum 
It's a pity , Moods , but you have a mistake here ...
You see , all this "energy exchange" between the coil and the target occurs via the same magnetic field , being reduced with the distance by the same 6-th power law . So we cannot "cheat" the nature and get some additional gain . What we really have from the target is two kinds of the signal - one signal is a "momentary" target reaction ( also called "X-component" ) , and a "delayed reaction" ( also called "R-component") . Classic PI detector does receive only R component and ignores X , and this is why it has all its properties - good ground tolerance and absence of ferro-discrimination . But when you begin to measure the signal during your A and B periods - you will capture this X-component too .... and of course , this signal cannot be 1000 times stronger than that you had measured before in your PI - if it would , than every IB detector ( that utilizes X signal by its principle ) will kill every PI machine 1000 times too - but we don't see it , anyhow . And it doesn't depend on the coil damping method , because the main process ( eddy current start and decay ) occures in the target , very loosely coupled to the coil .
But what you will get if you do this ( completely ignore this eddy current signal in a C period ) ? Of course , you will get a detector that in some situations can be more sensitive than a classic PI machine .... but this difference cannot be high , and another problem - you'll loose the "ground tolerance" ( ground balance ) of your device , because the best sensitivity it will have only to a ferrite target - that gives the most strong X-signal . Another kind of targets that this circuit would feel well is a superconductor target , being the "ideal opponent" to a ferrite ... but we cannot meet it in a real situation , of course . So , if we want to make a perfect wideband detector , we must use all signal energy that the target does return , converting our device to the kind of "optimal receiver".... of course , it's too long to explain now , but once I wrote it on the page 3 of this Geotech topic - http://www.geotech1.com/forums/showt...nduction/page3 - I explained there the main difference in signal processing between IB and PI machines , and also explained how to use all their advantages simultaneously ...
It's a pity , Moods , but you have a mistake here ...
You see , all this "energy exchange" between the coil and the target occurs via the same magnetic field , being reduced with the distance by the same 6-th power law . So we cannot "cheat" the nature and get some additional gain . What we really have from the target is two kinds of the signal - one signal is a "momentary" target reaction ( also called "X-component" ) , and a "delayed reaction" ( also called "R-component") . Classic PI detector does receive only R component and ignores X , and this is why it has all its properties - good ground tolerance and absence of ferro-discrimination . But when you begin to measure the signal during your A and B periods - you will capture this X-component too .... and of course , this signal cannot be 1000 times stronger than that you had measured before in your PI - if it would , than every IB detector ( that utilizes X signal by its principle ) will kill every PI machine 1000 times too - but we don't see it , anyhow . And it doesn't depend on the coil damping method , because the main process ( eddy current start and decay ) occures in the target , very loosely coupled to the coil . But what you will get if you do this ( completely ignore this eddy current signal in a C period ) ? Of course , you will get a detector that in some situations can be more sensitive than a classic PI machine .... but this difference cannot be high , and another problem - you'll loose the "ground tolerance" ( ground balance ) of your device , because the best sensitivity it will have only to a ferrite target - that gives the most strong X-signal . Another kind of targets that this circuit would feel well is a superconductor target , being the "ideal opponent" to a ferrite ... but we cannot meet it in a real situation , of course . So , if we want to make a perfect wideband detector , we must use all signal energy that the target does return , converting our device to the kind of "optimal receiver".... of course , it's too long to explain now , but once I wrote it on the page 3 of this Geotech topic - http://www.geotech1.com/forums/showt...nduction/page3 - I explained there the main difference in signal processing between IB and PI machines , and also explained how to use all their advantages simultaneously ...
Do you have the complete schematic of the Moodz detector so that we can all analyse it and thus test the validity or otherwise of your assumptions about it?
In another words , when you hope to get a 1000 times more sensitivity due to utilize this "instant reaction target signal" ( X-component ) , that classic PI don't use - this is a MISTAKE , because this signal cannot be 1000 times stronger with a real metal target , anyhow .
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