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Magnets only really effect VLF detectors and they will sound off like a Hot Rock, they don't normally effect PI machines unless they have a metal casing like the ones in that picture.
Rare Earth Magnets
- Thread starter Goldbuzzhashit
- Start date
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Flowerpot said:aussiefarmer said:Six magnets not three sorry
https://www.prospectingaustralia.co...3499459_img_20160821_140327_661-optimized.jpg
Carrying it over the shoulder there was almost zero interference on the sdc but at waist height there was warbles.
I seen a rake with a magnet on every tooth once .
That looks like the bees knees aus, I should ask do the magnets stay on the pick all the time? ( Ha that's better silver
They are actually riveted on but that was over kill because they are powerful enough to stay there, be careful playing with neodymium / rare earth magnets as they will fly together and shatter or pinch your skin and when they shatter eye damage is likely as they pretty much explode into pieces.
Those $2 coin sized magnets i have on the pick will stick to each other through my palm , so one on back of hand, one in palm. Powerful.
malri_au
Steve
lol,whats that a 50kg?
here's me,pulling cars out a river:
j/k.haha.
here's me,pulling cars out a river:
j/k.haha.
silver said:It'll only get the visible surface steel at any rate flowers..... would serve a purpose in a high steely area that overlies a truly great researched site that's gunna give if you can get to it (no Windows) ,.... it's the up down that provides some good exercise within our passivity (I pick up visible rubbish anyway).
Not just steel - it picks up many of those noisy iron pisolites as well (that polished-looking buckshot ironstone),
but I suspect would take all day to do this with a magnet. Does anyone know why the ironstone causes problems (I'm guessing but suspect it might be the maghemite in the ironstone, which being magnetic much like magnetite, has its own magnetic field which would distort the magnetic field of your coil, giving a false reading - I doubt if it is its electrical conductivity of the ironstone that is the problem, since that is only moderate). Magnetite would do the same, but the most common iron mineral (limestone = goethite) is not magnetic and is a poor electrical conductor, so is less of a problem.
I'm assuming this because I think a gold detector works on the principle of gold being an excellent conductor rather than a mediochre one - when the magnetic field from your coil swings across gold it would induce current flow in the gold and that would create a secondary magnetic field around the gold that distorts your coils field, giving a buzz (Eureka)! Basically by giving the resultant field a large resulting horizontal component. Although people talk about conductive ground I wonder if the issue is not more magnetic ground? Any experts on this out there?
If the magnetic field of the ironstone is the problem, even sweeping the surface with a rake or broom might help reduce noise and be faster than a magnet. Even where actual layers of ironstone gravel are present (so that the entire layer cannot be swept away just the loose pisolites), the magnetic type of ironstone is usually at surface only in places like Victoria, Tasmania and much of NSW because it is just iron-rich soil, and occurs as loose pisolites in sand. The iron-rich soil layer itself (including its pisolites) is usually not very magnetic because it is mostly limonite and hematite (not magnetic minerals). The maghemite is confined to the actual ground surface because it forms when bushfires dehydrate the previously limonite-hematite ironstone pisolites, turning them into magnetic maghemite (lower water content).
Places like WA (eg Eastern goldfields) and large parts of SA, Qld and NT (eg Tennant Creek) would be a different stiory unfortunately (two reasons - much of the ironstone is not soil but a different maghemite-magnetite rock, and secondly because much of the coarse gold concentrates in the ironstone. However most of Victoria, NE Tasmania, and areas like the Hill End and Tibooburra area in NSW would not have this issue despite having noisy ironstone - areas with what geologists call "orogenic gold"
I may be talking through my hat in arguing from theory - can anyone tell me ("you're up yourself goldierocks!")?
malri_au
Steve
you mention conductivity,but not frequency resonance which is what matters most in what gets detected and what doesn't.ie;does it bounce? is it content or mixture enough to bounce in the right range.
malri_au
Steve
your coil is after all,an antenna.
malri_au
Steve
that would depend on the detectors capability. ^
malri_au
Steve
maybe confused words of conductive with conducive? your coil is not zapping the ground. you are not detecting the magnetic field,you are sending a signal and waiting for a response,tx/rx,transmit/receive. you balance the field so that magnetic field doesn't affect the sending/receiving as much,trying to get minimal distortion.the magnetic field will change the movement of signals,this is the need for ground balancing.
And I am discussing induction as well as conduction. Apparently two frequencies are not used.
This description seems to be saying much what I am, but assumes it is all due to conductivity difference in the target. What I am querying here is whether it really is just conductivity difference (betwen ironstone versus gold or copper in a coin) or whether it is actually the maghemites' natural magnetic field (ferromagnetism) that causes the main problem (maghemites field at surface, which is where it occurs in large llumps in abundance, might be far greater than typical of the induced field at many centimetres depth in gold or copper). A magnetic field is a magnetic field, it does not matter how it is generated, only how strong it is and its orientation (vertical versus horizontal, which is why a horizontal coin responds better than a vertical coin - a horizontal conductor moving through a vertical field distorts the field more than a vertical conductor moving in a vertical field).
I am guessing that the detector detects the distortion of its own field (however this distortion occurs) by a different current being generated in the detector compared to what it produces itself - perhaps a voltage change - sounding a buzzer or moving a meter needle proportionally to that distortion? The fact remains that there is only one field that can be measured at your detector, distorting the field it has generated, whether the distorting field generated by the target is natural ferromagnetism of the target or a field induced by the current flow your detectors field induces in the target.
I'm certainly no expert and might be wrong, but my father (who founded his own electronics company) made me a metal detector in about 1965 to encourage my interest in geology - after working with mines in the Pacific war - since then I just use them. If it were ferromagnetism causing the false readings rather than just conduction in ironstone, I can also think of an even better way to solve the problem that beats a broom or a magnet.
Being a practical man as well, I will try a broom before and after on noisy ground. ]
This description seems to be saying much what I am, but assumes it is all due to conductivity difference in the target. What I am querying here is whether it really is just conductivity difference (betwen ironstone versus gold or copper in a coin) or whether it is actually the maghemites' natural magnetic field (ferromagnetism) that causes the main problem (maghemites field at surface, which is where it occurs in large llumps in abundance, might be far greater than typical of the induced field at many centimetres depth in gold or copper). A magnetic field is a magnetic field, it does not matter how it is generated, only how strong it is and its orientation (vertical versus horizontal, which is why a horizontal coin responds better than a vertical coin - a horizontal conductor moving through a vertical field distorts the field more than a vertical conductor moving in a vertical field).
I am guessing that the detector detects the distortion of its own field (however this distortion occurs) by a different current being generated in the detector compared to what it produces itself - perhaps a voltage change - sounding a buzzer or moving a meter needle proportionally to that distortion? The fact remains that there is only one field that can be measured at your detector, distorting the field it has generated, whether the distorting field generated by the target is natural ferromagnetism of the target or a field induced by the current flow your detectors field induces in the target.
I'm certainly no expert and might be wrong, but my father (who founded his own electronics company) made me a metal detector in about 1965 to encourage my interest in geology - after working with mines in the Pacific war - since then I just use them. If it were ferromagnetism causing the false readings rather than just conduction in ironstone, I can also think of an even better way to solve the problem that beats a broom or a magnet.
Being a practical man as well, I will try a broom before and after on noisy ground. ]
malri_au
Steve
the detectors own field would be a known constant,it's the earth/grounds that changes,hence what needs to be adjusted/ground balanced.and why some ground is too hot or needs working differently.
malri_au
Steve
this is a good convo actually,because it brings me to another point of detectors,which is voltage and battery mods.
we've all seen what happens when more power is able to be used,increased depth.
so my question is,'how big are your batteries and what volts do they out?'
the other thing I want to throw out there is using an oscilloscope to visually see what the signal looks like.
not enough money yet to fund my crazy science.one day.
we've all seen what happens when more power is able to be used,increased depth.
so my question is,'how big are your batteries and what volts do they out?'
the other thing I want to throw out there is using an oscilloscope to visually see what the signal looks like.
not enough money yet to fund my crazy science.one day.
Yes, which is basically what I am saying although I did not (and do not) know how one "tunes out" noisy ground. Does one simply balance out the typical field over noisy ground with gold absent, and hope to see the difference when gold is present? That sounds far too crude and insensitive - it must be some frequency method dependent on the different frequency response of the two types of material surely, as I suggested originally?
I am trying to work this out to determine if ferromagnetism can be an additional factor, since in the end you are still measuring a resultant induced field, and there would be a large horizontal area of non-attenuated ferromagnetism at surface (presumably the target's field is also furhter attenuated coming up through the ground because of the ground's dielectric properties)? The question is not whether conduction in the target is the principal mode of detection but whether ferromagnetism at surface decreases the sensitivity of detecting it to the point of some areas being undetectable as a result (and whether that is fully appreciated or whether the simple conductivity of ironstone is assumed to account for it all - the target response and all the noise). If so there would be a way to virtually completely overcome that I suspect, but it would possibly slow the rate of covering ground slightly and significantly increase the price of detectors (assuming it is not what is actually being used in newer detectors).
I am trying to work this out to determine if ferromagnetism can be an additional factor, since in the end you are still measuring a resultant induced field, and there would be a large horizontal area of non-attenuated ferromagnetism at surface (presumably the target's field is also furhter attenuated coming up through the ground because of the ground's dielectric properties)? The question is not whether conduction in the target is the principal mode of detection but whether ferromagnetism at surface decreases the sensitivity of detecting it to the point of some areas being undetectable as a result (and whether that is fully appreciated or whether the simple conductivity of ironstone is assumed to account for it all - the target response and all the noise). If so there would be a way to virtually completely overcome that I suspect, but it would possibly slow the rate of covering ground slightly and significantly increase the price of detectors (assuming it is not what is actually being used in newer detectors).
malri_au
Steve
oscilloscope being able to see which frequencies need filtering out.
The oscilloscope would be no problem and they are made small for use on ground proton precession magnetometers which are on a similar arm and held in front of you much like a metal detector. WHich is why I was talking frequencies and thinking things like pulsing and subtracting fields.
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