Mike Hillis
Well-known member
That issue isn't about depth. It isn't about sensitivity to small targets or conductors. It isn't about recovery time or iron masking or construction. The one issue we focus on is about one target. Steel bottle caps.
Here is a good link to steel bottle cap construction from the Coinstrike Homepage: Even though the CoinStrike is the machine being referenced, the bottle cap information is relevant to all machines.
http://home.insightbb.com/~johnhetti/coinstrike/bottlecaps.htm
The T2 likes to read steel bottle caps up into the high coin range. Not all of them but enough that we focus on them. Most machines show these as zinc range targets with the occasional one that hits high coin. Why does it like to do this?
Per Dave Johnson
"The things we did in the T2 to achieve its excellent target separation, deep and repeatable target ID, and quickness of response, also conspire to make bottle caps look like coins. "Third derivative discriminators" such as are found on a couple Fisher models tend to exhibit somewhat this same combination of strengths and weakness. A rule of thumb on rejection of flat iron is that the broader a footprint you use to look at it, or the more you smear its response, the easier it is to reject it. Unfortunately these same things compromise nonferrous discrimination and ID."
Now that this target has been focused upon, we have learned of several ways to correctly id this target.
1. In maximum discrimination, the T2 causes the audio to click on the steel bottle cap.
2. The FE3O4 bargraph spikes over the steel bottle cap.
3. The pinpoint mode gives a broader response over the steel bottle cap vs a coin.
4. Taking a moment to center and bob the coil over steel bottle caps will cause the TID number to fall further than a coin will.
5. The Discrimination 3b Audio Mode is designed to cause the steel bottle caps to give a more bouncing TID number than a coin.
Per Dave Johnson
"In the regular 3 mode steel bottle caps will usually give a one-way response if they're tilted, but if they're laying flat they can hit solid and consistent every pass, the way a coin does. What the 3b mode does, is to make them bounce around a lot more even when they're lying nearly flat. A coin will usually act the same in 3 or 3b. If you search with "# OF TONES" selected in the menu, when you locate a questionable target you can use the knob to toggle back and forth between 3 and 3b to see the difference."
6. Tilted Steel bottle caps will give a lower TID number or tone response on a 90 degree turn. If you do the X pattern walking in a circle around a coin, you'll usually get nearly the same response all the way around. In the case of a steel bottle cap, if it's tilted, you'll tend to get one-way high tone responses in two quadrants of the circle, and medium and/or low tones in the other two quadrants.
As all of us current T2 owners and future T2 owners spend more time in the field with them using these methods, we will find the bottle cap discussion changing to favorite methods rather than "this is a problem"
One last generic comment on steel bottle caps. In new areas we like to cherry pick through them. In old areas we dig them because of masking.
Happy
Mike
Here is a good link to steel bottle cap construction from the Coinstrike Homepage: Even though the CoinStrike is the machine being referenced, the bottle cap information is relevant to all machines.
http://home.insightbb.com/~johnhetti/coinstrike/bottlecaps.htm
The T2 likes to read steel bottle caps up into the high coin range. Not all of them but enough that we focus on them. Most machines show these as zinc range targets with the occasional one that hits high coin. Why does it like to do this?
Per Dave Johnson
"The things we did in the T2 to achieve its excellent target separation, deep and repeatable target ID, and quickness of response, also conspire to make bottle caps look like coins. "Third derivative discriminators" such as are found on a couple Fisher models tend to exhibit somewhat this same combination of strengths and weakness. A rule of thumb on rejection of flat iron is that the broader a footprint you use to look at it, or the more you smear its response, the easier it is to reject it. Unfortunately these same things compromise nonferrous discrimination and ID."
Now that this target has been focused upon, we have learned of several ways to correctly id this target.
1. In maximum discrimination, the T2 causes the audio to click on the steel bottle cap.
2. The FE3O4 bargraph spikes over the steel bottle cap.
3. The pinpoint mode gives a broader response over the steel bottle cap vs a coin.
4. Taking a moment to center and bob the coil over steel bottle caps will cause the TID number to fall further than a coin will.
5. The Discrimination 3b Audio Mode is designed to cause the steel bottle caps to give a more bouncing TID number than a coin.
Per Dave Johnson
"In the regular 3 mode steel bottle caps will usually give a one-way response if they're tilted, but if they're laying flat they can hit solid and consistent every pass, the way a coin does. What the 3b mode does, is to make them bounce around a lot more even when they're lying nearly flat. A coin will usually act the same in 3 or 3b. If you search with "# OF TONES" selected in the menu, when you locate a questionable target you can use the knob to toggle back and forth between 3 and 3b to see the difference."
6. Tilted Steel bottle caps will give a lower TID number or tone response on a 90 degree turn. If you do the X pattern walking in a circle around a coin, you'll usually get nearly the same response all the way around. In the case of a steel bottle cap, if it's tilted, you'll tend to get one-way high tone responses in two quadrants of the circle, and medium and/or low tones in the other two quadrants.
As all of us current T2 owners and future T2 owners spend more time in the field with them using these methods, we will find the bottle cap discussion changing to favorite methods rather than "this is a problem"
One last generic comment on steel bottle caps. In new areas we like to cherry pick through them. In old areas we dig them because of masking.
Happy
Mike