Tony sent me some Ferrite. Here is what I found.....

[Digger]

Several days ago, tony (Orlando, FL) asked why his X-Terra 30 would read a piece of ferrite as -4 in the all metal mode and not register it at all in the Pattern mode with all notches accepted. I thought about that for a few days, and responded that I believed it was due to the X-30 notches not being capable of reading the ferrite. I told him that I didn't have a piece of ferrite to prove or disprove my theory. But I believed that the ferrite must be "lower" than -4 and his X-30 couldn't register what it was while in the pattern mode. I look at notches as being able to either accept or reject certain targets. Simply turning all the notches to accept does not mean that it will detect all metals. It only means that it will detect those metals whose content happens to fall into one of those notch segments. I figured it hit it in all metal, because it is simply a conductor. I also figured it read as -4 in all metal because it was being detected, and -4 is as low as the LCD would register. Even though he had all the notches accepted in his discrimination (pattern) mode, I didn't think the X-30 would be able to detect a substance with less conductivity than -4. That was my theory anyway.

Well, Tony was nice enough to send me a piece of his ferrite, and I received it today. This evening, I put it through some tests with several of my current detectors. Here are my results and some thoughts as to why???

X-30 all metal reading: -4
Pattern with all notches accepting: no reading

X-70 all metal reading: -8 with flashes of +48
Pattern with all notches accepting: -8

XLPro all metal reading: audible tone and no meter movement
discrimination mode reading: audible tone with discrimination level
adjusted to Grd Rej or lower. No meter movement. Any setting higher
than Grd Rej resulted in no tone.

Advantage all metal mode: clear audio response
discrimination mode at lowest setting: no audio tone

Garrett 1350 zero discrimination mode: audio tone with TID at max (12)

DeLeon all metal mode: clear audio (VCO) response
discrimination mode with minimum discrimination - slight chirp

Explorer II set at zero iron mask gave readings of 31 / 31


From these results, I believe that the ferrite sample used has properties that place it in the " -8 category" of the X-Terra series. And, as I suspected, the X-30 will only read targets as low as -4 while in a pattern mode. When the X-30 is able to obtain an audio in the all-metal mode, it displays a -4 in the LCD because again, that is as low as the meter is capable of displaying. The X-70 has the capability of reading "down to" -8. And this piece of ferrite did read -8 in both all metal and the pattern mode.

Regardless of some recent comments on the forum, I found an article published by Whites, instructing users of internally ground balanced detectors (when hunting in a hot rock area) to properly adjust the ground balance level with the use of ferrite. They go on to say that, if you don't have ferrite, you can make changes by bobbing the coil. I remember tweaking the GB on an IDX Pro that I use to have. (peel back the flag sticker and turn the trimmer knob with a small screwdriver) Although the XLPro that I have has auto Ground balance, I am inclined to believe that Whites uses ferrite to establish the "base setting" for the Ground Rejection position on the discrimination level markings. That is why I can read the ferrite in the all-metal GEB, and only up to the point marked "Grd Rej" while in GEB discrimination mode.

Both of my non-metered detectors have adjustable discrimination, and neither surprised me with their results. I have used the Advantage long enough to not let anything it is capable of doing surprise me! By picking up the ferrite in all metal mode, both detectors indicate that their all-metal mode must be "all-metal" and not just another version of a zero discrimination mode.

The X-70 confirms another theory I have about discrimination. Most people look at discrimination levels as a straight line. From least to highest. I prefer to look at discrimination levels as circular instead of linear. For example, a circle is comprised of 360 degrees, with 0 being the same as 360. If you think of discrimination being circular instead of linear, you will find that the highest discrimination level setting is adjacent to the lowest level setting. That is why, when the ferrite measures -8 in the all metal mode of the X-70, it also has flashes of +48. The maximum possible reading at each end of the spectrum. Highest and lowest. And, when I switched to pattern with all notches accepted, it only reads the -8. Why??? Because I am only accepting segments of targets and not all possible metallic targets, as I do when I am in the all metal mode. People can say what they want about the X-Terra all metal mode actually being a zero discriminate mode. And, not being part of the design team or an engineer, I don't know for sure. But this ferrite test indicates to me that the all metal mode is capable of detecting virtually any metal that you can put in front of it. And that is close enough to all metal for the type of hunting I do.

I will make mention of the fact that the Garrett 1350 does not have an all metal mode. It offers notch discrimination and provides a zero discrimination mode. I have to think that the Garrett notches are designed a bit differently than the X-70 in that the ferrite would not read on the lower end of the spectrum. Only the highest end at a 12. Again, I attribute this to discrimination being circular instead of linear, and the 1350 notch parameters being different than the X-70.

If you have any questions or comments, fire away. Again, I am not an engineer. Just a guy who likes to metal detect and tries to learn as much as I can about the equipment I use. Thanks to Tony for sending me the ferrite to make these tests and comparisons. HH

Randy

 

[Jackpine Savage]

Digger,

Have you compared all metal vs -4 accepted on the X-30 on various ferrous targets to see is there actually is a difference in iron acceptance levels? Also you need to compare the two modes with some hot rocks.

Is the 30 threshold based like the 50 and 70? If not, that could provide a clue as well.

Don't rule out the possibility of some offset in GB between the 2 modes.

Tom

 

[Digger]

Tom, You raise some good questions and interesting possibilities. Other than running some tests and reporting the results, I don't have any answers. When I first read the posts about ferrite and how it reacts to the X-30, I have to admit I really didn't see the point! As I said, I don't have any ferrite and would prefer to GB my detectors on site, with the current soil conditions. However, now that I have made some comparisons between various makes and models, I can see variances in how they are designed and built. I didn't find any differences that would affect the type of coin hunting I do around here. But for those hunting in soil with extreme mineralization levels, it might.

I did wave several old iron objects under the coils and they all read ferrous maximus. That is interesting because most of them read a good signal when buried or I wouldn't have dug them in the first place. I think we have all been there with deep iron. Although the readings were different between the various models of detectors, they did remain consistent within the ranges expected by ferrous targets. Those with larger notch segments did not provide as many different readings, naturally. And, as expected, target ID was affected by sweep speed, distance from the coil and size of the target.

Let me reiterate, this is by no means a scientific experiment. I was simply testing a piece of ferrite with my X-30 to see if it read consistent with what Tony's read. It did. Then, I compared it to several other makes and models in an effort to explain why I think it did.

I recently sent my X-50 into Minelab for some repair work. I wish I had it back, as it could answer a couple questions I have remaining. Since the numeric reading goes lower on it than either the X-30 or the X-70, it could better define that piece of ferrite Tony sent me. And, since it is most like the X-30 in design, it might give me more basis for my theory. Or totally confuse me!!! HH Randy

 

[Captain Kirk]

Digger,

One of the big differences between ferrite and iron is that ferrite is designed to have as low (ideally zero) a conductance as possible. The reason for this is to reduce eddy current power dissipation in the core.

Another point is that generally ferrite has lower permeability than iron. So iron and ferrite are two rather different "animals". I think that ferrite (albeit rather concentrated) may a reasonably good representation of iron dust in ground.

HH,
Glenn

 

[Digger]

Ferrite is magnetic, like iron or steel, but it is not a conductor of electricity. However, for a given size core, ferrite material will saturate at a much lower magnetic flux density than one made from iron powder. Permeability for ferrite materials ranges from 20 to 15000 while for iron powder it is from 2 to 75. As a "rule of thumb", the higher the permeability of the material the greater will be the temperature coefficient. Ferrite materials can be divided into two groups: those with initial permeabilities below 1000 which are nickel-zinc compounds and those above 1000 which are made from manganese-zinc compounds. Nickel-zinc ferrites exhibit high volume resistivity, moderate temperature stability and can offer high Q factors for the 0.5 to 100 MHz frequency range. They are well suited for low power, high inductance applications, and their high permeability factors make them very useful for wideband transformer applications. The manganese-zinc group have relatively low volume resisitivity and moderate saturation flux density. They can give high Q factors for the 1 kHz to 1 MHz frequency range, and some are sutiable for switched-mode power conversion transformers operating between 20 and 100 kHz. Incidently, the high permeability iron powder core made from 26 or 52 material is particularly suitable for the filter inductor in switched mode power supplies.


But again, I am not an engineer. I'm too old to go back to college. But I plan to stay in a Holiday Inn this weekend. LOL Thanks. HH Randy

 

[Captain Kirk]

n/t

 

[Digger]

and ran it through the same test, with the same piece of ferrite that Tony sent me. The X-50 will read the ferrite as a -9 in both the all metal mode and in Pattern one, with all notches accepted. HH Randy

 

[tony (Orlando FL)]

Hey Randy,

You are sure giving that ferrite a workout, thanks for your efforts.

Is -9 the lowest the x-50 can display?

Tony

 

[Digger]

And I also confirmed your comment on not hitting a tone in PP mode. In fact, you can hear blanking when you pass over the ferrite in PP. HH Randy