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question on coil separation .
- Thread starter Nock
- Start date
MarkCZ
Well-known member
Well I'll try and tackle this one. LoL!
Larger coils cover more ground and can gain some extra depth, but at a cost. The larger coverage means if the area is well littered with metal objects then your likely to get more of them in the detection field at one time. When this happens the processor has to attempt to process them at the same time, with about any detector this causes some problems.
Now a much smaller coil has more of the ability to move around amongst the objects without having as many in the field of detection at the same time, doing this would mean the smaller coil would help "Better Separate" the targets. But keep in mind that the smaller coil doesn't cover as much ground as the larger one and some depth may be lost.
Now, to get around this somewhat the manufactures has tried other ideas to try to come up with the best of both worlds, like the "Oval Coil" (elliptical coil),
3"x6"
4"x6"
5"x10"
ect...
With these coils you get could ground coverage while at the same time you can get fewer items in the field of detection.
Mark
Larger coils cover more ground and can gain some extra depth, but at a cost. The larger coverage means if the area is well littered with metal objects then your likely to get more of them in the detection field at one time. When this happens the processor has to attempt to process them at the same time, with about any detector this causes some problems.
Now a much smaller coil has more of the ability to move around amongst the objects without having as many in the field of detection at the same time, doing this would mean the smaller coil would help "Better Separate" the targets. But keep in mind that the smaller coil doesn't cover as much ground as the larger one and some depth may be lost.
Now, to get around this somewhat the manufactures has tried other ideas to try to come up with the best of both worlds, like the "Oval Coil" (elliptical coil),
3"x6"
4"x6"
5"x10"
ect...
With these coils you get could ground coverage while at the same time you can get fewer items in the field of detection.
Mark
TerraDigger
New member
Picture a deflated ballon under your coil. This is your electro-magnetic field.
Now start adding air to the balloon. As more air is added, the balloon no longer fits between objects in the ground. Add enough air and the balloon covers multiple objects at the same time.
Each type of coil produces a 'balloon' of varying size.
When the 'balloon' fits between targets it is able to identify 'each' target. When the balloon covers multiple targets, it no longer see's individual targets and cannot identify them correctly.
Size of coil & it's design determine the balloon size/shape.
Now start adding air to the balloon. As more air is added, the balloon no longer fits between objects in the ground. Add enough air and the balloon covers multiple objects at the same time.
Each type of coil produces a 'balloon' of varying size.
When the 'balloon' fits between targets it is able to identify 'each' target. When the balloon covers multiple targets, it no longer see's individual targets and cannot identify them correctly.
Size of coil & it's design determine the balloon size/shape.
Critterhunter
New member
People sometimes get confused about recovery speed, separation, and discrimination level, in terms of what they each do to all add up to unmasking ability. Really unmasking ability is a combination of all three of these factors, and so they all play an important part in it but for very different reasons. And, if one is lacking it can be compensated for by the others to still add up to good unmasking ability.
Separation, plainly put, all falls down to how sharp the detection field of the coil is to see the good and not the bad beside it. Separation boiled down to it's purest meaning is the ability of the coil to see the good and not the bad right next to it. At first this may sound wrong to people but if you think about it this is the most exacting description of separation ability. It's all about the coil and how sharp it is.
Recovery speed is an issue if you like to sweep faster, so make sure then that you are using a fast recovery machine in that case. With a slow recovery speed you need to compensate for it by slowing down your sweep speed.
Some other pros/cons in how these all relate to each other in terms of the sum of unmasking ability are for instance....Recovery speed does not automaticly mean better separation. A fast machine can be using a rather dull bulky coil detection field and thus have no real better ability to see between targets. The key to separation, again in it's purest form or description, is the sharpness of the coil's detection field. Recovery speed can of course alter the ability of the machine to see between targets, but this is all dependent and addressable by your sweep speed. Use a slow sweep on a slow machine and it's largely a non-issue.
I think of discrimination level in other terms than probably most people. Many think say for instance that low or no iron rejection gives the machine more ability to "see" a coin mixed with iron at the same time. I think this is wrong myself. I personaly don't believe the machine has the ability to see both at the same time, unless they are laying at the same depth and right up against or on each other.
Rather, with lower iron rejection there is less lag time between the two targets...As the machine doesn't have to go from "rejection mode" of the discriminated out iron to "accepting mode" of the accepted coin. There is a certain lagish processing that takes place in a machine from going from one to the other, so by accepting iron it's staying in "accept mode" and thus ready to sound off more readily when it sees the coin next.
However, lacking the ability to lower iron rejection on some machines, you are then forced to find other ways to increase unmasking ability. Mainly, to me that would be using a "sharper stick", or in other words a coil such as the 12x10 that has a very sharp DD detection line. That or a small coil of course. It gives the machine more time to distinctly go from "seeing" to "not seeing" the iron, and so it has more time to reset from rejection mode and be ready to accept the coin.
In a sense it's in effect speeding up recovery speed, but not really. It is, though, giving the machine more time to reset from seeing the iron and so be ready to see the coin. Kind'a like cleanly turning the page in a book, so that it's ready to read or see the coin on the next page.
We've played with high iron rejection with a "regular coil" versus a low setting but using a sharp detection field on the 12x10, and surprisingly (never would have believed it myself) the outcome of both on the same undug targets has been exactly the same in how those coins were seen. Until I saw this with my own eyes and ears I would have thought the only true way to unmask better was by lower iron rejection, but now I see there are two ways to skin that cat. Not saying one way is better or has more merit than the other, just saying that at least what I've seen so far has been a total wash between the two.
In summary, recovery speed can be address by proper coil use and speed. Discrimination level can also be addressed by proper settings. Separation can not be changed by how the user sets up or uses the machine, but rather by coil choice. All three play important roles and I wouldn't argue that one is more important than the other. Just that there are several paths to reach unmasking Utopia.
Separation, plainly put, all falls down to how sharp the detection field of the coil is to see the good and not the bad beside it. Separation boiled down to it's purest meaning is the ability of the coil to see the good and not the bad right next to it. At first this may sound wrong to people but if you think about it this is the most exacting description of separation ability. It's all about the coil and how sharp it is.
Recovery speed is an issue if you like to sweep faster, so make sure then that you are using a fast recovery machine in that case. With a slow recovery speed you need to compensate for it by slowing down your sweep speed.
Some other pros/cons in how these all relate to each other in terms of the sum of unmasking ability are for instance....Recovery speed does not automaticly mean better separation. A fast machine can be using a rather dull bulky coil detection field and thus have no real better ability to see between targets. The key to separation, again in it's purest form or description, is the sharpness of the coil's detection field. Recovery speed can of course alter the ability of the machine to see between targets, but this is all dependent and addressable by your sweep speed. Use a slow sweep on a slow machine and it's largely a non-issue.
I think of discrimination level in other terms than probably most people. Many think say for instance that low or no iron rejection gives the machine more ability to "see" a coin mixed with iron at the same time. I think this is wrong myself. I personaly don't believe the machine has the ability to see both at the same time, unless they are laying at the same depth and right up against or on each other.
Rather, with lower iron rejection there is less lag time between the two targets...As the machine doesn't have to go from "rejection mode" of the discriminated out iron to "accepting mode" of the accepted coin. There is a certain lagish processing that takes place in a machine from going from one to the other, so by accepting iron it's staying in "accept mode" and thus ready to sound off more readily when it sees the coin next.
However, lacking the ability to lower iron rejection on some machines, you are then forced to find other ways to increase unmasking ability. Mainly, to me that would be using a "sharper stick", or in other words a coil such as the 12x10 that has a very sharp DD detection line. That or a small coil of course. It gives the machine more time to distinctly go from "seeing" to "not seeing" the iron, and so it has more time to reset from rejection mode and be ready to accept the coin.
In a sense it's in effect speeding up recovery speed, but not really. It is, though, giving the machine more time to reset from seeing the iron and so be ready to see the coin. Kind'a like cleanly turning the page in a book, so that it's ready to read or see the coin on the next page.
We've played with high iron rejection with a "regular coil" versus a low setting but using a sharp detection field on the 12x10, and surprisingly (never would have believed it myself) the outcome of both on the same undug targets has been exactly the same in how those coins were seen. Until I saw this with my own eyes and ears I would have thought the only true way to unmask better was by lower iron rejection, but now I see there are two ways to skin that cat. Not saying one way is better or has more merit than the other, just saying that at least what I've seen so far has been a total wash between the two.
In summary, recovery speed can be address by proper coil use and speed. Discrimination level can also be addressed by proper settings. Separation can not be changed by how the user sets up or uses the machine, but rather by coil choice. All three play important roles and I wouldn't argue that one is more important than the other. Just that there are several paths to reach unmasking Utopia.
Critterhunter
New member
Critterhunter said:
Meant to say low iron rejection with a "regular coil" versus a high setting but using a sharp detection field.
Again, many people will find one of these three factors (separation, recovery speed, or discrimination level) more important to them than others, so I don't argue that one is more important than the other. Largely that's based on the strengths and weaknesses of the machine being used and thus what you need to address or improve on to enhance unmasking ability. The only thing I would conclusively argue is that the most important thing is the ability of the coil to separate by way of a sharper or smaller field. Everything else is built on top of that foundation, and that's were there are then several paths to take to reach the end results. Again, those paths are largely dependent on what your machine can and can't be changed about, and so you may be forced to improve one or the other to reach the final goal. Any one of these three factors can be improved when others can't, to enhance the end result.
Critterhunter
New member
A bit controversial in terms of even how I always thought about the factors involved in unmasking for years. Certain in field tests on undug targets has opened my eyes to other ways unmasking can be improved when certain things involved can't. Just saying there are several things involved, and each play a different but equally important role (separation, recovery speed, and discrimination level). One can compensate for the other when it can't be changed. For example, if your machine is unable to lower discrimination to accept all iron, then by using a sharper or smaller detection field from what I've seen it can seemingly do just as well as a low or no iron rejection but not using as coil with as sharp of a detection field, or a smaller one of course. Also, since you can't change recovery speed on most machines, you can change your sweep speed as well as how you use the coil to sniff between targets to make it pretty much a non-issue. Know the strengths or weaknesses of your machine and then try to address one of the three things to increase unmasking in ways that you can alter. Just remember that the foundation that it all is built on is how good the coil can "see" between targets.