Jump to content
Steve Herschbach

Fisher Impulse AQ Discrimination Explanation

Recommended Posts

Skate.... like me you are going to have to dig most on the high end and low end until u have confidence in what it maybe.   I just don’t want to be in AM then switch to disc .... and have the machine disc out a 24k 8 gram ring.... that may have been heard clearly in AM.   I’m assuming when the digital comes out we may have the ability to adjust the NOTCH 

Share this post


Link to post
Share on other sites

Steve , back on your diagram page 6 ( the modified version of a Minelab Equinox chart for the AQ), there is something which is not clear to me with this chart :

In summary , this shows shows the PI detection scale like this, from left to right :

1. Small ferrous /     2. AQ detecting range /   3. Iron nails , screws  /  4. large ferrous

I do not understand why there is an "iron gap" between 1.small ferrous  and  3. iron nails, screws.

Why no ferrous in this 2. AQ detection range?

There should be some ferrous of intermediate sizes between 1.small ferrous and 3.iron nails,. And no void as it is indicated in the chart. And at end I think that the AQ will accept some ferrous , just my opinion … 

thanks for your answer , Alain

Share this post


Link to post
Share on other sites

Hi Alain,

I went ahead and deleted the post and the chart. I put several disclaimers in the post that the chart was for conceptual purposes and was not intended to create an absolutely detailed, accurate, and definitive target response chart. I was assuming some degree of interpretation/interpolation by the viewer. Part of the problem is it is being taken out of the context of everything I have posted on the subject in the last ten days. I explained previously in this thread ahead of the chart that ferrous covers the entire range so I obviously agree with your conclusion since I have explained that exact thing so people would know it to be the case. I included both ends of the ferrous range in the chart and did actually include a portion of the bottle cap range that you must have missed. Long story short since the chart is being taken as definitive instead of conceptual despite the disclaimers, leaving it up is misleading or confusing people, and so deleting it it is probably for the best. I halfway knew when I posted it this was going to happen.

  • Like 2

Share this post


Link to post
Share on other sites
15 minutes ago, Steve Herschbach said:

I went ahead and deleted the post and the chart.

too late that my screen saver on my PC and the screen is huuuuuuuge :fisher:

 

RR

  • Haha 1
  • Oh my! 1

Share this post


Link to post
Share on other sites

Ok Steve but I think that your initial idea is good , such a detailed chart is very interesting because it is very simple to understand so I think that fisher labs should provide one in the AQ user manual , so that people know exactly what the AQ can do ( or not do ) . This will avoid a lot of misunderstandings and frustations . Also from what I read here the AQ is a new generation machine that works differently from the previous ones and everything must be very well explained. 

BTW unfortunately for me , it looks like the AQ is not adapted for moderated mineralization ground prospecting  ( I am a coin shooter, inland  ) , so I will have to wait the future Fisher RELIC machine , I hope it will come soon because the VLF machines do not evolve any more in terms of depth performance since several years and I need some extra depth    :-) ... 

Thanks for everything , Alain

 

  • Like 1

Share this post


Link to post
Share on other sites

I agree Alain about a chart, and I have a good start on one, but without actually having a detector it's only educated guesswork on my part based on what Alexandre and LE.JAG have posted so far. The one I posted was just a quick and dirty illustration. Hopefully they or Fisher will do something official before release, otherwise you can be sure people will eventually construct some at a later date.

I was hoping for one detector that would do both land and sea, something I liked about my ATX. To be honest I think Fisher will have a hard time making a detector more powerful than a GPX 4500 or GPX 5000 let alone a GPZ 7000, and few people who already own those are willing to give up any power, even if the detector is lighter and costs less. Minelab means gold prospecting to a lot of people so Fisher has a tough road ahead there, and they have let Minelab have lots of advance notice what to expect.... I doubt the engineers down under are asleep at the wheel. The AQ model however has only a couple detectors, the Garrett ATX and Beachhunter TDI, that are truly equivalent product. For me at least, having none of the three at the moment, the choice is pretty clear. I am fed up with 7 lb detectors that have $500 coils, and the Impulse, using the TDI as a starting point, simply has to be better, or Fisher has wasted a lot of time and money. I sent Dave Johnson a TDI (big box version) years ago and Carl worked at White's so they know what they need to beat to succeed.

fisher-impulse-aq-vs-garrett-atx-vs-whites-tdi.jpg
Fisher Impulse AQ vs Garrett ATX vs White's TDI Beachhunter

  • Like 3

Share this post


Link to post
Share on other sites

This discussion has been great, but just like the Equinox original threads, when you run out of new information, it gets a little repetitive. I'm hoping it will not be the same long wait that Minelab had. After reading everything about the machine, I am torn on, if it can do better than my GPX? If there are not enough deep rings available, than I would probably run it so it can pick up the widest range of targets (hopefully as high as silver too). I understand that I will be digging large and small iron, and also I understand that I will never get that small thin gold, (like chains and stamped charms) because of the locked salt setting. But I'm starting to worry that I will be digging a ton of deep pull tabs and very little gold. The deepest decent sized gold ring (14K) I have found with the GPX was around 12-14". A small woman's 10K ring was a wobbly reading at around 12" Can it do better than that, is what I am wondering now.

 

Share this post


Link to post
Share on other sites

Note that the TDI PULSESCAN no longer exists

Share this post


Link to post
Share on other sites
5 minutes ago, ALEXANDRE TARTAR said:

Note that the TDI PULSESCAN no longer exists

New anyway. Here is a used one for $700

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 Whitbey
      The way to go Steve H,
      I also let it go, no AQ for me anymore they lost me as a client, looking into the Aussie detector QED even without service in the US, when having problems I just send the pot in for service to Down under land, only concern I have is it needs certain adjustment/tuning, for use in gold country in the US what I read.  Steve H. Can you tell me what adjustment the QED needs to used in our gold country. I would appreciate any information on this, so I can ask the Aussie maker of the QED to make these ajustments. See this as my experiment for 2020 /2021, I also wouldn't mind to lend my QED as a test machine to you or any other experienced nuggett hunter for experiment testing.
      Just want to tell you that I am not a dealer or interested in selling any detectors to prevent any misunderstandings,  wanted to do this pet project for a few years. Better do it now and don't want to postpone any pet projects, life is short and I don't know if the COVID19 virus gets me this year or next year! No waiting for me anymore, it' now or never!
    • By Rom14
      a new video by Le Jag
       
       
       
    • 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 BigSkyGuy
      Many of you have expressed a desire to know how well the Impulse AQ will function for land use. One option is to wait until the unit is released. I know, no fun! The other option is to analyze the information we do have on the unit and on PIs in general, combined with information from the scientific literature and various forum posts. I have done such an analysis which is a bit long, but I will summarize the findings followed by how I arrived at the conclusions. The places where I believe the unit will be effective include the following:
      Black sand beaches (mainly coarse unweathered magnetite)
      Soils containing mildly weathered granite and other felsic igneous rocks (I know this appears to conflict with Alexandre’s post, but I will elaborate below)
      Unweathered or mildly weathered basic igneous rocks (basalt, gabbro, etc.)
      Places where I think the AQ will struggle include:
      Weathered basalt and soils derived from basalt
      Some fine-grained volcanic rocks such as rhyolite.
      The basis of my groupings above is the published magnetic susceptibilities (MS) for various minerals and rock types and on the concept of frequency dependent MS which is a very important consideration for PI detectors.
      MS is a measure of the magnetization of a material in response to an applied magnetic field. Frequency dependence is when the measured MS varies when different frequencies are used for the induced field. Minerals with high MS are responsible for the “mineralization” when speaking of metal detector performance. Three minerals are responsible for most “mineralization”; magnetite (Fe3O4), titanomagnetite, and maghemite (ꝩ-Fe2O3). The MS for these minerals are orders of magnitude higher than for other iron minerals such as hematite (α-Fe2O3), goethite, biotite, pyroxenes, etc. The relative proportions of these minerals within different rock types determines the MS of the rock. Ranges for different rock types are shown in the table below.
      Rock Type
      Magnetic Susceptibility Range (10-6 SI)1
      Andesite
      170,000
      Basalt
      250-180,000
      Diabase
      1,000-160,000
      Diorite
      630-130,000
      Gabbro
      1,000-90,000
      Granite
      0-50,000
      Peridotite
      96,000-200,000
      Porphyry
      250-210,000
      Pyroxenite
      130,000
      Rhyolite
      250-38,000
      Igneous rocks
      2,700-270,000
      Average felsic igneous rocks
      38-82,000
      Average basic igneous rocks
      550-120,000
      Quartzite
      4,400
      Gneiss
      0-25,000
      Limestone
      2-25,000
      Sandstone
      0-20,900
      Shale
      63-18,600
      1.       Compilation from Hunt et al. (1995)
       
      Minerals with high MS are responsible for the poor performance of VLF metal detectors. Hematite within soils is typically red, but given the relatively low MS, is not particularly problematic to metal detectors. So, red soil is not always bad!
      The MS of soil is a function of the parent rock from which it was formed (see table) and the degree of weathering of the iron minerals present. Soils formed from basic igneous or volcanic rocks such as basalt generally have higher MS than soils formed from felsic rocks (rhyolite, granite, etc.), but it depends on the specific rock. For example, some granites have low MS because they are dominated by ilmenite (S-type granite) as opposed to magnetite (I-type granite). Ilmenite has low MS. Geologists use MS to map different types of granite. Da Costa et al. (1999) found that the basic volcanic rocks from southern brazil produced soils containing maghemite (high MS) and hematite while the intermediate to felsic volcanic rocks produced soils containing goethite (low MS). However, there are examples of basic rocks having low MS and felsic rocks with high MS, it all depends on the mineralogy, the grain size, the degree of weathering, subsequent geochemical reactions during and after soil formation, and other factors.
      Typically, the smaller the grain size, the higher the MS. Therefore, a volcanic rhyolite which has a much smaller grain size than its intrusive equivalent granite, will have a higher MS even for an identical magnetite content. Smaller magnetite particles also weather faster than coarser grains. Magnetite can weather to maghemite on exposed outcrops. Maghemite is an earthy mineral that forms very small grains. The small grains produce a superparamagnetic domain which results in frequency-dependent MS which causes problems for even PI metal detectors, especially PIs which do not have the ability to ground balance (such as the Sand Shark and Impulse AQ). Magnetite can also form very small grains, and if small enough can also be superparamagnetic. However, magnetite tends to be coarse-grained while maghemite tends to be very fine-grained.
      Maghemite tends to form from magnetite and other minerals in tropical climates or where tropical climates once existed. The “bad ground” in Australia is due to the presence of maghemite, which is a brown to brick red mineral. Maghemite is less common in the US but is present. Magnetic anomalies found at the National Laboratory at Oak Ridge TN were found to be natural deposits of iron-bearing colluvium (sediment which has accumulated at the base of a mountain range) which has oxidized to maghemite (Rivers et al., 2004). Maghemite and hematite can be created from goethite (α-FeOOH) in response to the heat generated by forest fires and slash and burn agriculture (Koch et al., 2006). Therefore, poor detecting conditions can be created in such areas.
      The bad ground at Culpepper VA is probably due to maghemite, but I have seen no information to confirm this. Geologic maps of Culpepper Co. do show the presence of basic bedrock, such as basalt and dolerite.
      The granite that Alexandre mentioned as giving the Impulse AQ problems may be an I-type granite (magnetite rich) in which the magnetite has partially weathered to maghemite.
      The reasons for why I think the Impule AQ will or will not work in various soils/rock types is summarized below.
      Soil/Rock Type
      AQ Works?
      Reason
      Black sand layers on beach
      yes
      Black sand is derived from physical weathering of igneous and metamorphic rocks in upland areas and consists mainly of relatively unweathered magnetite.
      Soils derived from felsic igneous rocks
      probably
      Felsic igneous rocks with high MS, tend to be coarse grained and even when dominated by magnetite (I-type) do not typically produce maghemite unless highly weathered.
      Soils derived from basic igneous rocks
      Probably not
      Soils derived from basic igneous rocks tend to be dominated by maghemite.
      Basic igneous hot rocks
      maybe
      Basic igneous rocks such as gabbro can be a problem if weathered or partially weathered to maghemite.
      Felsic igneous hot rocks
      probably
      Unless highly weathered, felsic rocks are dominated by magnetite which the AQ should be able to handle
      Volcanic hot rocks or black sand beaches (i.e. Hawaii)
      maybe
      If fresh, the main source of MS is magnetite. If weathered or partially weathered to maghemite, the AQ may have problems. If very fine grained even unwethered volcanic rocks may present a problem.
       
      References
      Da Costa, A.C.S, Bigham, JM, Rhoton, FE, and SJ Traina. 1999. Quantification and Characterization of Maghemite in Soils Derived from Volcanic Rocks in Southern Brazil. Clays and Clay Minerals, v. 47, no. 4, p. 466-73.
      Hunt, CP, Moskowitz, BM, and SK Banerjee. 1995. Magnetic Properties of Rocks and Minerals. In Rock Physics & Phase Relations: A Handbook of Physical Constants, Volume 3.
      Koch, C.B, Borggaard, OK, and A. Gafur. 2005. Formation of iron oxides in soils developed under natural fires and slash-and-burn based agriculture in a monsoonal climate (Chittagong Hill Tracts, Bangladesh). Hyperfine Interact 166, 579–584.
      Rivers, JM, Nyquist, JE, Terry, D.O., and W. E. Doll. 2004. Investigation into the Origin of Magnetic Soils on the Oak Ridge Reservation, Tennessee. Soil Science Society of America Journal, Vol. 68 No. 5 p. 1772-1779.
    • 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?  
×
×
  • Create New...