A
Anonymous
Guest
Hi,
I'm looking to PI as the future in metal detecting, with discrimination being the main area for improvement.
I currently own two "discriminating" PI detectors. My Minelab GP 3000 has an iron id "blanking" feature that causes the signal to cut out on shallow iron/steel targets. This feature has gotten some poor reviews from some but I have found it to be reasonably effective at handling areas with lots of shallow trash, particularly for nugget detecting. It can be inaccurate but so can all discrimination systems. It's main drawback is an inability to work at depth.
My Garrett Infinium has a dual tone id system that roughly splits items into low conductive and high conductive. Anything above zinc penny (copper penny on up) on a VLF scale read low tone. Zinc penny or lower on the VLF scale reads high tone. The wild card is that since the Infinium is a PI unit, long skinny steel items like nails and hairpins plus exceptionally rusted flat steel read high tone, while most larger steel items read low tone. While the system has limits, for nugget or jewelry detecting digging high tones gets you the gold while ignoring many iron/steel trash items. For coin detecting digging low tones gets you copper pennies, and all silver and clad coins while ignoring most common trash along with nickels and zinc pennies. Some good older finds like Indian Head pennies will also get left behind digging low tones. Again, the Infinium system is rudimentary at best, but I find it beats nothing, and it does appear to work at depth.
So is this it for availability right now? I'm afraid I'm not counting so-called "reverse discrimination" systems as they simply act like sensitiivity controls in my experience. As you advance the amount of "reverse discrimination" less conductive items and deeper items are tuned out. The theory is to dig items that drop out as the control is advanced, and ignore those that continue to signal. Items like jewelry and nuggets will tend to drop out, large trash will continue to signal. But I found that large trash items at depth act like low conductive targets and so drop out, and are then dug. Conversely, a shallow ring or large nugget will continue to signal, and so be ignored following this general "reverse disc" rule. In general I have found reverse disc to act no better as a discimination system than would a system using the sensitivity contol on a VLF machine. It's only real use seems to be in setting a unit to ignore tiny shallow items, although with an attendant loss of depth on larger, edge of detection depth items.
The methods used on the GP 3000 and Infinium are audio type discrimination systems that require no manipulation of controls by the operator. Just listen and make your call as to whether to dig or not. Both systems allow you to hear all targets, so the decision to dig is still left to the operator, as it should be. There certainly are times when operator judgement will say "dig anyway" despite what the disc system is saying. When in doubt, dig it out!
Although it is little documented, the Minelab SD/GP detectors exibit a similar dual tone response on targets. This is strictly separate from the iron id system and works whether it is engaged or not. Most nuggets tend to give a high tone, and many iron items a low tone. On both the SD/GP detectors and the Infinium a large enough gold nugget can give a low tone response, as exhibited by some nuggets in Jack Lange's fabulous video series on the Minelab machines. But so far all nuggets I've tested up to 6 ounces have given high tones, so it has something to do with nugget composition and the amount of ground mineralization.
Since these are "ground balancing" PI detectors the high or low tone responses most likely change with the ground balance setting. I've been told this dual tone id may be directly related to the ground balancing system. Do any other PI units have such a response? The only other PI unit I have experience with is the Surf PI, and it has a mono tone response.
Garrett advised me that changing the setting on the reverse discrimination (pulse delay) control also can have an effect on where the high/low split occurs. I've not yet has time to experiment with this.
The photo shows the results with the Infinium in pea gravel under shoolyard equipment, digging all items. Left items are high tone, right items are low tone. Most gold nuggets and jewely items would fall in the left hand batch if they were present. The surprise for me was how digging low tones resulted in more coins than trash, at least for this locale.
While nugget detecting I've had almost opposite results. The left hand side would be almost all nuggets, with a few thin, elongated nails. The right hand side would be a pile of large iron and steel items.
Needless to say, I'm anxiously awaiting the fabled "Pulse Devil". It's winter here in Alaska right now, but when the snow melts I plan on doing more "dig it all" tests and will post pictures of how the the systems split the finds.
Final note... no one need point out how digging it all gets finds missed by id systems. What I'm lobbying for is better pulse id systems, and trying to learn how to best leverage those that exist to my advantage.
Steve Herschbach
I'm looking to PI as the future in metal detecting, with discrimination being the main area for improvement.
I currently own two "discriminating" PI detectors. My Minelab GP 3000 has an iron id "blanking" feature that causes the signal to cut out on shallow iron/steel targets. This feature has gotten some poor reviews from some but I have found it to be reasonably effective at handling areas with lots of shallow trash, particularly for nugget detecting. It can be inaccurate but so can all discrimination systems. It's main drawback is an inability to work at depth.
My Garrett Infinium has a dual tone id system that roughly splits items into low conductive and high conductive. Anything above zinc penny (copper penny on up) on a VLF scale read low tone. Zinc penny or lower on the VLF scale reads high tone. The wild card is that since the Infinium is a PI unit, long skinny steel items like nails and hairpins plus exceptionally rusted flat steel read high tone, while most larger steel items read low tone. While the system has limits, for nugget or jewelry detecting digging high tones gets you the gold while ignoring many iron/steel trash items. For coin detecting digging low tones gets you copper pennies, and all silver and clad coins while ignoring most common trash along with nickels and zinc pennies. Some good older finds like Indian Head pennies will also get left behind digging low tones. Again, the Infinium system is rudimentary at best, but I find it beats nothing, and it does appear to work at depth.
So is this it for availability right now? I'm afraid I'm not counting so-called "reverse discrimination" systems as they simply act like sensitiivity controls in my experience. As you advance the amount of "reverse discrimination" less conductive items and deeper items are tuned out. The theory is to dig items that drop out as the control is advanced, and ignore those that continue to signal. Items like jewelry and nuggets will tend to drop out, large trash will continue to signal. But I found that large trash items at depth act like low conductive targets and so drop out, and are then dug. Conversely, a shallow ring or large nugget will continue to signal, and so be ignored following this general "reverse disc" rule. In general I have found reverse disc to act no better as a discimination system than would a system using the sensitivity contol on a VLF machine. It's only real use seems to be in setting a unit to ignore tiny shallow items, although with an attendant loss of depth on larger, edge of detection depth items.
The methods used on the GP 3000 and Infinium are audio type discrimination systems that require no manipulation of controls by the operator. Just listen and make your call as to whether to dig or not. Both systems allow you to hear all targets, so the decision to dig is still left to the operator, as it should be. There certainly are times when operator judgement will say "dig anyway" despite what the disc system is saying. When in doubt, dig it out!
Although it is little documented, the Minelab SD/GP detectors exibit a similar dual tone response on targets. This is strictly separate from the iron id system and works whether it is engaged or not. Most nuggets tend to give a high tone, and many iron items a low tone. On both the SD/GP detectors and the Infinium a large enough gold nugget can give a low tone response, as exhibited by some nuggets in Jack Lange's fabulous video series on the Minelab machines. But so far all nuggets I've tested up to 6 ounces have given high tones, so it has something to do with nugget composition and the amount of ground mineralization.
Since these are "ground balancing" PI detectors the high or low tone responses most likely change with the ground balance setting. I've been told this dual tone id may be directly related to the ground balancing system. Do any other PI units have such a response? The only other PI unit I have experience with is the Surf PI, and it has a mono tone response.
Garrett advised me that changing the setting on the reverse discrimination (pulse delay) control also can have an effect on where the high/low split occurs. I've not yet has time to experiment with this.
The photo shows the results with the Infinium in pea gravel under shoolyard equipment, digging all items. Left items are high tone, right items are low tone. Most gold nuggets and jewely items would fall in the left hand batch if they were present. The surprise for me was how digging low tones resulted in more coins than trash, at least for this locale.
While nugget detecting I've had almost opposite results. The left hand side would be almost all nuggets, with a few thin, elongated nails. The right hand side would be a pile of large iron and steel items.
Needless to say, I'm anxiously awaiting the fabled "Pulse Devil". It's winter here in Alaska right now, but when the snow melts I plan on doing more "dig it all" tests and will post pictures of how the the systems split the finds.
Final note... no one need point out how digging it all gets finds missed by id systems. What I'm lobbying for is better pulse id systems, and trying to learn how to best leverage those that exist to my advantage.
Steve Herschbach