Span Limit & Wrap Limit Questions. . .

[TC-NM]

In simple terms, can someone give me an answer to what does Span Limit and Wrap Limit do in the Discrimination mode? What affect does it have with any other settings?

Thank,

TC-NM

 

[CyberSage]

This is not only a function of the discriminate mode, but specifically the Correlate mode. The Correlate mode looks for two frequencies to agree on a response from a target. The criteria for determining whether two frequencies agree is how close the VDI response matches. This "how close" condition is determined by the Span Limit The larger the span limit the more accepting the response trigger is to the VDI response of the target between those two frequencies. The Wrap Limit allows the Span setting to extend to the negative side. Deep targets can cause the higher two frequencies to "Wrap" around to the negative side. I have even seen all 3 frequencies wrap in high EMI scenarios, or improperly nulled coils. These settings are among the most powerful options on the V3/V3i.

Jack

 

[Rob (IL)]

Just got my internet back. Thanks for the good explanation Jack.

 

[CyberSage]

Your welcome Rob. Sorry about your Internet connection. Welcome back.

Jack

 

[nw1886]

Span and wrap can help with slightly deeper gold chain too. If your signal is longer and -2/3, dig! Chain is there (just not seen
by most equipment and settings). Span and wrap does help.

 

[Larry (IL)]

I don't know if Span would help with -2, -3, but I think Wrap is limited to the -95 to -90 range.

 

[CyberSage]

That's how I understand it Larry. The wrap setting only affects the circular effect at the high end of the scale. -95 to -90.

 

[nw1886]

Guess I just don't understand it correctly then? Was hunting in a newer park,with lots of fill from presumably an old home site (old residential types of bits and pieces....and iron. Thinking Wrap was for the lower end too, set to correlate and adjusted. Went on to find two nice chunks of broken 14K! I'm going to have to work with it more "while" understanding it?!! (Guess it's a 360 degree thing/of course!) Thanks for the check. Guess that leaves copper, bronze, and silver from a complex matrix?

 

[Larry (IL)]

You might be right Scott, I haven't messed with it much. This is a good question for Anne. For those interested, this is what is in the manual:

Correlate

 

[Rob (IL)]

For sure the wrap has nothing to do with better response in the -2/3 range. The span won't do anything different than it would for any other VDI span range. Since correlate will, "reject targets without reasonable similarities expected of good quality metals" it might help by eliminating small trash signals making the chains a little more noticeable ??

 

[ak_1234]

Since my name got mentioned, I'll respond. But I have nothing to add over what Jack said. He has it spot on.

 

[TC-NM]

Thanks Cybersage for the explanation and all that responded. I do have a couple of questions though. Would it be beneficial if in 'Wrap Limit' to have it OFF in +94 +95 <and> -95 all the way through 0 zero so there is no wrap occurring? Would this help in better distinguishing silver better in the high numbers (82 to 94)? I hoped I asked that right?

TC-NM

 

[ak_1234]

Thanks Cybersage for the explanation and all that responded. I do have a couple of questions though. Would it be beneficial if in 'Wrap Limit' to have it OFF in +94 +95 <and> -95 all the way through 0 zero so there is no wrap occurring? Would this help in better distinguishing silver better in the high numbers (82 to 94)? I hoped I asked that right?

TC-NM

I'm not sure I understand your question correctly. But, wrap limit is a limit on how far past +95 the target can wrap with a maximum limit of -90. So if you have a silver dollar that would ring in at +91 in air, but with soil conditions and EMI, might come in at -93, setting your wrap to -92 would allow that silver dollar to be seen. As an example, say 7.5k is reading your silver dollar at +94 and your 22.5k is reading at -93. With wrap off, those 2 VDIs are too far apart to be seen as a good target (a difference of 187), unless you have the span set to >187. With wrap on and set to -92, that allows the 22.5k VDI to be unwrapped. And in this example, if you have span set to 5 or more, this would allow the silver dollar to be seen as a good target. You don't want to make span too tight or you will miss targets due to variations on external conditions. You can open it up all the way, and then all targets will correlate, but not as easy to cherry pick. But wrap will not go all the way to 0, your range is limited from -95 to -90.

I don't know your conditions, so I can't tell you if wrap off would help or not. If your targets tend to shift, you might want to have it on as your good targets on the high end may wrap around. But, if not, then turning it off may help remove more of the junk.

 

[Rob (IL)]

Boy, I don't know what more can be said to explain it. You will still have to experiment to set the span and wrap to your conditions. That is not something we can do for you.

[size=large]A big thank you and hello Anne[/size]. By the way the on board manual does a great job of explaining this.

[attachment 187133 cop.gif]

 

[TC-NM]

Boy, I don't know what more can be said to explain it. You will still have to experiment to set the span and wrap to your conditions. That is not something we can do for you.

[size=large]A big thank you and hello Anne[/size]. By the way the on board manual does a great job of explaining this.

[attachment 187133 cop.gif]

No, No, No rcasio44 and AK_1234! You all that responded gave a clear picture here. Like you said, I'll have to experiment with my settings.

Thanks,

TC-NM