Positive impulse or Negative?

[Luc]

Hi,
I see DEVOUT outlines of with mosfet that they supply impulses high tension
I placed or denied to you to you,
then you knowing the type of answer who have several the ferrous metals and not ferrous
to these impulses therefore if those metals answer strongly with echo pi
eno employee from the polarity ?
One synthetizing,
than difference between supplying to a ferrous or not ferrous metal
a positive impulse or negative, that metal answers in the same way?
Thanks.

[Luc]

Re: Positive or Negative Impulse from PI ?

Hi,
(repeat)
Than difference between supplying to a ferrous or not ferrous metal
a positive impulse or negative, that metal answers in the same way?
Thanks.

Sorry for my bad english.

[Reg]

Re: Positive or Negative Impulse from PI ?

Hi Luc,

I am not sure anyone has spent any serious time trying to analyze the signals from a positive and negative pulses.

However, George Payne's 1978 patent indicates one can distinguish some differences, especially if the object is close. See the following link:
http://www.thunting.com/geotech/pages/metdet/patents/US4110679.pdf

Now, this patent uses triangular pulses and can distinguish some differences.

Sorry, but that is about all the info I can supply.

Reg

[Cossaro Fernando]

Re: Positive or Negative Impulse from PI ?

The effect in the target, induced by the coil,is the same.

If you consider the magnetic field generated from a positive pulse as North-South, the inversion of polarities generate an indentical magnetic field South-North.

Consider that if you have PI planar coil, simmetrical and perfectly planar, the sensitivity at upper side is identical at lower side.

By the prospective of the target, if in the top of the coil you have a magnetic field NS, at the other side you have SN. The same effect obtained by the inversion of the pulse polarities.

[Cossaro Fernando]

Re: Positive or Negative Impulse from PI ?

If you alternate a positive pulse with a negative pulse the isteresis for an iron metal object is different and can be detected.

[Luc]

Re: Positive or Negative Impulse from PI ?

Thanks Reg !

[KT315]

Re: Positive or Negative Impulse from PI ?

I can simply change wire ends of coil... and the polarities ALSO will change.

yours

[Luc]

Re: Positive or Negative Impulse from PI ?

Hi Fernando,
in effetti mi riferivo ad una bobina che viene pilotata da 2 impulsi di +/-400v distanti di un certo deltaT in modo da rilevare 2 informazioni diverse (naturalmente alla stessa profondità!)

[Carl-NC]

Re: Positive impulse or Negative?

By themselves, positive & negative pulses will give the same response. But, as Cossaro said, what happens when you alternate pulses?

Specifically, what would you get if you compare the response of a positive pulse, with the response of a positive pulse that was immediately preceded by a negative pulse? Intuitively, you would expect a different result if the target is ferromagnetic, due to hysteresis. But I expect it to depend on the target decay rate and the timing of the negative pulse. It might be difficult to set up.

I had started building a circuit to look at this some time ago, but got stuck on getting the H-bridge to work, and never got back to it.

--Carl

[Luc]

Re: Positive impulse or Negative?

>By themselves, positive & negative pulses will give the same response. But, as Cossaro said, what happens when you alternate pulses?

That one is the point


>Specifically, what would you get if you compare the response of a positive pulse, with the response of a positive pulse that was immediately preceded by a negative pulse? Intuitively, you would expect a different result if the target is ferromagnetic, due to hysteresis. But I expect it to depend on the target decay rate and the timing of the negative pulse. It might be difficult to set up.

>I had started building a circuit to look at this some time ago, but got stuck on getting the H-bridge to work, and never got back to it.

>--Carl

Excuse, hard work to understand, use the H bridge?
I use a circuit similar to the licence us2002/0050822a1, but with mosfet P and N, at least in spice simulation.
Carl Thanks!

[Cossaro Fernando]

Re: Positive or Negative Impulse from PI ?

Ciao, come ho gia' detto in questo caso interviene la curva di isteresi propria del materiale. Molto piu' larga nei ferro-magnetici e strettisima nel metalli diamagnetici. Questo e' quello che ricordo di elettronica-fisica nel calcolo del fattore di merito di una bobina.
In pratica la larghezza dell'isteresi dissipava internamente al target energia per via delle correnti indotte, che poi sono direttamente collegate alla diversa curvatura del segnale post-inpulso.

Presumo che utilizzando un segnale alternato si debba fornire un impulso di maggiore durata proprio per superare la curva di isteresi altrimenti vi e' solo dissipazione nel cambiamento di polarita' NS-SN indotto nel materiale. Ecco spiegato perche' nei bi-pulse hanno batterie supplementari.

Adesso traduci in inglese per quelli che non conoscono la nostra lingua (e mi scuso con loro per non conoscere alrettanto bene l'inglese).

[Cossaro Fernando]

Re: Positive or Negative Impulse from PI ?

...and you obtain the same effect.
I've described the concept in the MagneticField-TargetEffect prospective.

[Luc]

Re: Positive or Negative Impulse from PI ?

>Adesso traduci in inglese per quelli che non conoscono la nostra lingua (e mi scuso con loro per non conoscere alrettanto bene l'inglese).

>

Io proprio non lo so l'inglese...uso la toolbar di Alta****a.
Ciao e Grazie.

[KT315]

can you speak on English-Internacionalle pls? I do not make aware of, sorry (-)

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