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Help me understand the iron discrimination settings

Bill_S

Well-known member
The AT Pro has 40 iron disc settings. So how does that work? The higher the number the more iron it will knock out. So would the big pieces of iron need a setting of 40 to not be heard and a nail maybe a 10. Dont quite understand how it works. Why would you need a setting of 20 on the iron disc. Why hear some but not all iron? Any ideas? Thanks.
 
No it isn't based on size but rather the composition of the metal. Since I haven't used an AT PRO yet I can't say for sure where targets will fall on its scale, I can us a Teknetics T2 as an example as it also has a target ID scale where 1 thru 40 ID numbers are for iron. Well actually the 1 thru 10 numbers on a T2 go down into ground minerals as the lowest iron target I have found with one had a reading of 12. It seems to me that very rusty stuff will tend to have lower numbers than a similar object that isn't so rusty, so an old square nail in good condition might read a 22 to 24 but a very rusty one might get knocked down to 16 to 18. Also more crudely forged iron such as the stuff made in local blacksmith shops in the 1600s and early 1700s will tend to read lower than stuff made in the 1800s and and later in the 1700s. For example an early ox shoe might read 18 or so while one from the 1800s might read 25 or so just because the metal is better quality. Again using the T2 id scale I have found most nails read between 22 and 28 with machine made wire nails reading closer to 28 and older hand cut square nails tending to read around 22 though how rusty they are also changes the readings.

The shape of an iron target can also influence its reading with round washers getting upscaled because of their shapes. They can read higher on the iron and even go into the non-ferrous range. Although I go be the audio a lot more than the target ID numbers I tend to dig stuff that IDs below 20 and higher than 30. On the stuff between 20 and 30 I go by the sound. Once you learn the sound your detector makes (and I am not referring to "binary" audio as garrett refers to it as that doesn't give you any information besides what the target ID meter tells you) you can hear when something sounds like it should dug. For instance you learn that nails make a distinctive sound and when you come across an iron target with an ID between 20 and 30 that sounds different than the nail sound, then you dig it.

Personally, I am planning to set up my AT PRO (again this without the benefit of reading the manual yet, (Garrett if you read this please post the manual online so that those of us who pre-ordered it can begin studying it) by having PRO audio mode (of course) with the iron discrim set at 30 and with the iron audio enabled. According to my understanding this will make everything below 30 play an iron grunt and everything from 30 up to where the coins start play a middle tone and then the coins play a high tone. Personally all I need is two tones myself, one for iron and one for everything else as that is all you need for relics though those tones do need to be fully modulated with the real response from the target, not binary audio generated by the detector's processor based on its ID of the target.

The iron audio system is one of the features that makes it easy to see that the AT PRO was designed as a relic machine as the iron audio features would be useless to coin shooters and beach hunters 99% of the time as they would normally just notch out all of the iron and leave iron audio shut off.
 
Thanks for the explanation. It makes more sense now. I usually just hunt for coins so I discriminate all iron out. Couldn't understand why I needed so many segments for iron.....lol.
 
Bill,
I found the tiniest 14K child's gold ring 2 years ago. I was hunting in all metal with the 250. It hit mostly on iron but would hit the foil segment every 3 sweeps or so. It was so small I had an extremely hard time finding it even with the propointer! I would have passed on that target if it hadn't been the few times it hit foil. Now with 40 iron segments I can tweak that machine better to pick up small gold if I want. I can tell you that small gold definitely hits in the iron range. Depending on the iron "window" notch you may or may not dig some small gold or lead that you may be looking for?
 
The xterra 70 and Omega immediately come to mind. I have found small giold jewelry with each that did the iron foil bounce. I remember when the UK hunters panned the xterra 70 as not being sensitivie to their tiny cut hammered coins. Then they found out that the iron/foil bounce was where a lot of them hit.

Running at 15 Khz should help the sensitivity to small gold jewelry a lot so its possible most will come in the foil range without the iron bounce. The G2 I have been working has excellent TID lock on the small stuff but I have yet to hit any small gold in actual use. Did get a very deep mens band on a fresh water beach that in Disc mode gave only a slight tick in the audio and a very diggable signal in all metal.

Garrett has a great idea in the AT Pro and I applaud them for what they have done especially at its price point but the lack of a true all metal mode for some of us is a big deal.

Tom
 
Hey Tom by all-metal, I suppose you mean a static non-motion mode or
static VCO or SAT?
If they get the motion all-metal mode right, it may not be that big of a difference.
Anyway, the places I detect with all the iron trash, a static non-motion is fairly much useless.
 
Bill_S said:
The AT Pro has 40 iron disc settings. So how does that work?
The concept of a discriminate range spanning 0-40 isn't new. Teknetics T2 came out with that VDI break-down some 6+ years ago, and it is used on several other models from First Texas Products, such as the Teknetics Gamma and Omega, and the new Fisher Gold Bug and Teknetics G2. White's has provided broad-range acceptance or rejection and accompanying VDI numbers with their MXT and M6 and former models like the XLT or all those earlier 5900 & 6000 Di Pro or XL Pro models. Avid relic hunters, especially, and some savvy gold jewelry hunters, can appreciate having more adjustment control to accept or reject certain portions of the Iron ID range (0 to 40).

Metal detectors will detect metal, but the metal conductivity and detectability is related to the alloy content used, combined with the size and shape of the object. Target position will also have a bearing on the results of whether or not it might be detected with a higher or lower or inconsistent reading. Perhaps an excellent example is to say all Iron is not the same Iron. Even if two or three or four objects are made up in the same shape and contain equal parts of the same Iron, the readings will be different.

If that doesn't make sense, look at the other end of the detector's Target ID range. Note that all US 10
 
HI Steve I have never tried a detector with a static all metal mode. Can't remember if the T2 had one? Anyway motion all metal for me whether or not it has a self adjusting threshold, I have mild ground here.
 
Thanks for the detailed responses Monte and Steve. I think I have a better understanding now. :)
 
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