Mike Hillis or anyone else with White's V3i experience with dd and concentric coils

After using the Rutus Alter71 detector with concentric coil.
My first concentric coil I have ever used btw.

Can anyone comment please on the following.

The V3i model has a bottle cap reject setting, the Vx3 may too.

Does this setting on the detector basically work the same when using dd coil vs concentric coil?
Is bottlecaps reject even needed using concentric coil?

With and without bottlecaps reject setting levels applied.
Are there any differences noted on the spectrograph, and or polar plot and any other screen data displayed?

Btw I do have V3i experience but never had a concentric coil.
Sold unit long ago.



Edited 1 time(s). Last edit at 08/02/2017 11:16AM by Sod-buster.

Hi Sod-buster,
Thresholds are fairly easy to understand. Thresholds are most easily visualized as a horizontal line. Signals that respond below the line are not reported. Signals that response above the line are reported. This threshold horizontal line is mobile. It can be raised up or moved down thereby changing what signals responses can be reported or not reported. Fairly straight forward visualization of a threshold, yes?

This threshold visualization can apply to many things detector related, for example, Discrimination. Discrimination can be viewed as a Threshold setting where signals below the Discrimination line are silenced while things above the Discrimination line are reported on.

Bottle cap reject is a discrimination threshold setting that affects ferrous type responses and mostly comes into play when you get into a lot of flat ferrous, which includes bottle caps.

Now add this part….This threshold LINE can be thick or thin.

Coil types have an inherent bias, or predisposition that affects these Discrimination thresholds lines. They are either biased toward adding or toward removing a few points from this discrimination threshold line. Picture it this way. The coil type can make this threshold line thicker or thinner. Maybe you could even visuallize it as fuzzy or defined.

In this case speaking specifically to ferrous discrimination DD coils are negatively biased. They lower the discrimination threshold abilities of the detector. They make the threshold line thicker. Because of this, the operation of DD coils for some targets, in this case flat ferrous, required more detector design intervention. Ergo; Bottle Cap Reject settings, and/or a Polar plot in some of the Whites units, or BC (bottle cap mode) in some Fisher units, or the inclusion of a time report in the visuals displays in units such as the Rutus Alter71 or the AKA model hodographs.

The Concentric coil design doesn’t have this inherent negative bias toward the discrimination thresholds which in turn means less intervention is required to deal with such things as flat iron responses, bottle caps, etc. The concentric coil design gives a positive discrimination bias, basically tighter disc, they make the discrimination threshold line thinner, tighter, more defined.

To get to some of your questions, yes, BCR, Corrolate, all the graphs, including polar plot, and the operating modes respond differently depending on the coil type in use. Coil size also matters.

HH
Mike



Edited 1 time(s). Last edit at 08/02/2017 05:42PM by Mike Hillis.

Thanks Mike

Mike...thank you as well. Great reply. Learned a lot on that one.

Mike......... impressive! Clear. Well articulated.