earthmansurfer
11-20-2011, 01:34 PM
I hope you like to talk a little theory. I've been curious about these SEF coils and how they compare to the DD coils. I have heard they might be just a tad deeper, more quiet and perhaps more sensitive and on the V3i anyway - the ID might not be as consistent. Perhaps some of these differences depends on the detector though. Anyway, what really might the difference be? I came across an Italian metal detectorist's website and he posted some nice information on the SEF coils, siting some work by Carl Moreland (currently Chief Engineer of White's).
I'll post his google translated article but first will give my own quick understanding summary of it. Basically the signal transmitting and received by round (or oval) transmit/receive coils is more efficient than that shaped by ":grin: shaped coils. The ":grin: shaped coils have an area, where the half circle meets the straight line windings where there is an uneven magnetic concentration. This is the imperfection I believe.
I'm just posting this to pose the future of coils. It would be nice to hear any of your experiences comparing like sized DD coils with SEF as well.
It does seem like there have been some great advances with detectors and them having actually been with the coils. Most notably going from standard round coils to the newer DD designs. (To me there is a HUGE advantage under certain conditions). Well, I wonder what might be next out there? (Even outside coils) Anyway, here is the article. It is translated so not the best but it is quite clear to understand.
Enjoy,
Albert
SEF stands for Symmetric Electromagnetic Field (Symmetrical Electromagnetic Field) is a proprietary technology and the French Detec .
The plates SEF, also called butterfly has been produced for several models of MD (Garrett, XP, Minelab, White's, Fisher, etc.) and in various sizes from small 6 × 8 inch up to a huge 21 × 17. Who has tried these products supports a significant improvement in depth and in the management of mineralization than the standard plates concentric and DD.
Some define the SEF as variants of the plates Double D (WideScan) with the two coils instead of oval-shaped D.
Time ago I read an interesting post by Carl Moreland (currently Chief Engineer of White's) on this type of technology that I would like to summarize here.
Carl remembered that one of the most important things to get good results and reduce the effects of ground mineralization is related to having a good balance of induction (Induction Balance) between the transmitter and receiver coil ... well ... the so-called nulling
The plates are designed precisely so that this balance between TX and RX is the best possible. The more balance between TX and RX, the better the sensitivity of the machine.
The mineralization of the soil is primarily responsible for the so-called Ground Effect , ie the flattening of the electromagnetic field emitted by the transmitter coil. This deformation is detected by the coil RX (this is called pairing) and this implies a loss of balance, causing a loss of induction of performance and false signals.
According to Carl, theoretically speaking the best form of the coils to avoid this problem would be perfectly circular (OO) with an overlay similar to the DD. If the coils are perfectly round, the crushing of the electromagnetic field appears to be symmetrical and precise and if the deformation is symmetric coupling is minimal.
The advantage of OO compared to DD is that the latter, due to the large curvature of the intersections between straight and curved produce concentrations of magnetic field. This implies a field TX is not symmetrical and defined and hence a non-symmetric crushing.
If we look at the SEF will notice that the coils are not perfectly round and oval.
This form implies that, in the side where the curve is narrower (top and bottom) we are more concentrations electromagnetic but obviously not as dramatic as in the double D This, at the end of games, results in better management of mineralization compared to DD. Here is revealed their secret ...
I hope this helps ...
Bodhi3
Here is the original article (He has some other great articles if you care to use google translate or the like):
http://bodhi3.wordpress.com/2011/10/13/theory-i-segreti-delle-piastre-sef/
I'll post his google translated article but first will give my own quick understanding summary of it. Basically the signal transmitting and received by round (or oval) transmit/receive coils is more efficient than that shaped by ":grin: shaped coils. The ":grin: shaped coils have an area, where the half circle meets the straight line windings where there is an uneven magnetic concentration. This is the imperfection I believe.
I'm just posting this to pose the future of coils. It would be nice to hear any of your experiences comparing like sized DD coils with SEF as well.
It does seem like there have been some great advances with detectors and them having actually been with the coils. Most notably going from standard round coils to the newer DD designs. (To me there is a HUGE advantage under certain conditions). Well, I wonder what might be next out there? (Even outside coils) Anyway, here is the article. It is translated so not the best but it is quite clear to understand.
Enjoy,
Albert
SEF stands for Symmetric Electromagnetic Field (Symmetrical Electromagnetic Field) is a proprietary technology and the French Detec .
The plates SEF, also called butterfly has been produced for several models of MD (Garrett, XP, Minelab, White's, Fisher, etc.) and in various sizes from small 6 × 8 inch up to a huge 21 × 17. Who has tried these products supports a significant improvement in depth and in the management of mineralization than the standard plates concentric and DD.
Some define the SEF as variants of the plates Double D (WideScan) with the two coils instead of oval-shaped D.
Time ago I read an interesting post by Carl Moreland (currently Chief Engineer of White's) on this type of technology that I would like to summarize here.
Carl remembered that one of the most important things to get good results and reduce the effects of ground mineralization is related to having a good balance of induction (Induction Balance) between the transmitter and receiver coil ... well ... the so-called nulling
The plates are designed precisely so that this balance between TX and RX is the best possible. The more balance between TX and RX, the better the sensitivity of the machine.
The mineralization of the soil is primarily responsible for the so-called Ground Effect , ie the flattening of the electromagnetic field emitted by the transmitter coil. This deformation is detected by the coil RX (this is called pairing) and this implies a loss of balance, causing a loss of induction of performance and false signals.
According to Carl, theoretically speaking the best form of the coils to avoid this problem would be perfectly circular (OO) with an overlay similar to the DD. If the coils are perfectly round, the crushing of the electromagnetic field appears to be symmetrical and precise and if the deformation is symmetric coupling is minimal.
The advantage of OO compared to DD is that the latter, due to the large curvature of the intersections between straight and curved produce concentrations of magnetic field. This implies a field TX is not symmetrical and defined and hence a non-symmetric crushing.
If we look at the SEF will notice that the coils are not perfectly round and oval.
This form implies that, in the side where the curve is narrower (top and bottom) we are more concentrations electromagnetic but obviously not as dramatic as in the double D This, at the end of games, results in better management of mineralization compared to DD. Here is revealed their secret ...
I hope this helps ...
Bodhi3
Here is the original article (He has some other great articles if you care to use google translate or the like):
http://bodhi3.wordpress.com/2011/10/13/theory-i-segreti-delle-piastre-sef/