Jump to content
Steve Herschbach

Fisher Impulse AQ Discrimination Explanation

Recommended Posts

Understanding that this detector is designed primarily for saltwater detecting, how will it perform in freshwater?

Share this post


Link to post
Share on other sites

1 minute ago, Porky said:

Understanding that this detector is designed primarily for saltwater detecting, how will it perform in freshwater?

Even better since it has no technological limitation in this type of environment....

  • Like 5

Share this post


Link to post
Share on other sites

and in dry low/moderated mineralized ground ?

Share this post


Link to post
Share on other sites

Why use a PI on a low mineral beach? Unless you have an extra large coil there generally is no real depth advantage over a good VLF in low mineral ground and a VLF has far better discrimination.

I don’t even see the sense in testing one of these in Florida, as is being demanded by many people. This is a detector for the west coast or Hawaii, not Florida white sands. Florida is one of the worst possible test locations I can think of.

  • Like 4

Share this post


Link to post
Share on other sites

From a video that I saw it was a Manta if I remember well , it was able to detect a 2euros coin at 50cm ( 20inches) in wet sand of a sea beach , this test was done on a beach of Northern France . With a VLF such a coin is taken at max 30cm ( 12inches ) in moderated mineralized ground from my own tests . So you mean that a PI like the AQ could not go deeper than 30cm on such a big coin in moderated mineralized ground ?

I would be quite surprised with this because a VLF works exactly the opposite way, the depth performances of a VLF decreases while the ground mineralization increases. Nevertheless I have no real experience of PI prospectng apart a few tests done years ago with a GPX4500 , you know better than me on this subject …    Thanks for your answer again ...

Share this post


Link to post
Share on other sites

The depth performances of a VLF increases while the ground mineralization decreases.  Better explained this way ...

Share this post


Link to post
Share on other sites
7 minutes ago, palzynski said:

From a video that I saw it was a Manta if I remember well , it was able to detect a 2euros coin at 50cm ( 20inches) in wet sand of a sea beach , this test was done on a beach of Northern France . With a VLF such a coin is taken at max 30cm ( 12inches ) in moderated mineralized ground from my own tests . So you mean that a PI like the AQ could not go deeper than 30cm on such a big coin in moderated mineralized ground ?

I would be quite surprised with this because a VLF works exactly the opposite way, the depth performances of a VLF decreases while the ground mineralization increases. Nevertheless I have no real experience of PI prospectng apart a few tests done years ago with a GPX4500 , you know better than me on this subject …    Thanks for your answer again ...

No it is the opposite the more it is mineralized the more difficult it is.

But on the video you are talking about it is not very difficult for the PI, we do not consider this to be very mineralized.

But do not expect to detect the 2 euro coin more deeply.

It would take much stronger mineralization or magnetic soil to lose a few inches.

  • Like 2

Share this post


Link to post
Share on other sites
4 minutes ago, palzynski said:

The depth performances of a VLF increases while the ground mineralization decreases.  Better explained this way ...

It is the same thing for a PI but with low dimiunutions for the high-end.

  • Like 1

Share this post


Link to post
Share on other sites

Some people think a PI detects a lot deeper than a VLF and in the case of a very high power PI that can be true. But for what I would call mid-power PI detectors like the TDI SL or Garrett ATX, running off 8 AA batteries, the depth in low mineral ground running the same size coil is not much different than a good VLF. Assume just for illustration that a White's MXT with 12" coil and White's TDI SL with 12" coil get the same depth in mild ground on one particular test target.

Now we have a magic dial and can turn up the ground mineralization. As we increase the mineralization, both detectors lose depth. The MXT loses depth at a faster rate however. I can't give you an exact ratio, but you can reach a point where the TDI now goes much deeper than the MXT. Yet the TDI is still getting less depth also.... it just does not lose as much depth as quickly as the MXT.

It is also the case that with a PI if you have no ground balance filter engaged you can get the best depth in low mineral ground. Simply engaging the ground balance filter immediately robs a little depth. However, by engaging the control you do better in high mineral ground by comparison to the MXT. Whether you engage or disengage the ground balance circuit depends on the ground you are in.

PI detectors do best by comparison to VLF detectors when ground conditions are the worst. The milder the ground, the less good a PI looks by comparison to a good VLF, to the point where you are better off with a good VLF due to the superior discrimination. Where I am in Nevada a White's GMT or Goldmaster 24K or even MXT is a better all around gold prospecting detector than a White's TDI SL in a lot of the desert soils due to the mild ground conditions, and the hot VLF detectors can detect tiny gold nuggets a TDI can't see even in direct contact with the coil.

To sum up, the Impulse AQ will shine best where beach conditions are the worst. In general sands derived from volcanic activity and granitic rock, with high magnetic mineral content. People in mild sand derived from coral... not so much.

vlf-vs-pi-ground-balance.jpg

  • Like 3
  • Thanks 1

Share this post


Link to post
Share on other sites

Yes Alexandre and Steve , I agree with you , the more it is mineralized the more difficult it is to go deeper
this is what I wanted to say , probably I was not clear in my prev post.

Thank you Steve for the diagram , actually I did some measurements with a GPX4500 a few years ago and I could not get much than
13inches on a big coin in the air , a little less in my low mineralized ground. And you are right Steve this is not
far from a VLF machine which takes it at 12inches

But if we come back with the Manta video we are not talking about 13inches on a coin , but about 20inches which means a 54/100 increasement!
Even if there is a loss due to the mineralization , I would be happy with "only" 16 inches in my moderated mineralized ground,
this with a correct level of iron disc of course.

It looks like the AQ has something special to go so deeply, probably the delay to 7micros however I am
not a specialist.

thx again for your infos Alexandre and Steve 

For info my bed tests here :

 

 

 

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

  • Similar Content

    • By dewcon4414
      I think it will also be interesting to see what an aftermarket company might do with the 7uS coils.   Will we see more if this machine catches on?   Better yet will we see 7uS become the standard?   OR... is that a non-issue toward depth and sensitivity?  
    • By JEKOS123
      Hello Guys,
      I'm new on this forum and like Alexandre Tartar, I live in north of France.
      I was a young prospector in the 90's and asked my father (electronic engineer with good knowledge in magnetic field theory) to build a PI to hunt the beaches. So we have made, in a few months, an home-made PI metal detector 25 years ago, based on the technology of the old White's Surfmaster PI (mono coil). I remember the use of FETs (Field Effects Transistors to make 200 volts pulses). It worked, but unfortunately, my father was afraid by a so powerful magnetic fields and has continued his research on VLF detectors, until today !
      After this short presentation, here's my question :
      Is the Impulse AQ a bipolar detector ?
      Le Jag has explained us on the french forum "detecteur.net"  this technology developped by Alexandre :
      Positive and Negative pulse are alternatively sent.
      The positive one light the gold ring but magnetize the soil.
      The negative one demagnetize the soil.
      What about it ?
    • By PPP
      HI guys!
      It feels very good that this nice forum is at high speed with all discussions about the AQ with all different subjects about the AQ.We are now in the middle of january and still nothing from the Fisher.No reports from any tester, no videos, no manual, nada...it feels kind of depressing without knowing any informations at all.I know that LE.JAG and Alexander can't say anything about these informations even though the know for sure.Is there any thought or any guesses about these questions? 
    • By PPP
      I think the Garrett ATX challenges the AQ most and maybe TDIBH come close after ATX only in raw depth.I have myself an ATX and hunt my beach with it. Max sensitivity givs me around 15 inches for a normal coin size object.My Garrett sea hunter is absolutly no match and even my Equinox has no chance.The fair comparisson is ATX (PI , almost same coil size,waterproof ) I think the AQ has only one tone for both high and low conductive targets and one for iron.The ATX has one tone for high and one tone for low conductive targets but you have no tone for iron which makes one to digg all.
    • By fredmason
      I may have missed this issue..you know I am not very smart.
      will the prospecting, nugget finding version be wireless?
       I could not, would not buy another detector that doesn’t have a module.
      thanks
      fred
       
×
×
  • Create New...