Teknetics Forum

I watched a video today where a large silver coin was not detected during an air test but a gold ring and pull tab were.
I was wondering what might cause this phenomenon. I would direct you to the video but it has advertisement.

But here is the comment on this particular video

Metal detector circuit discriminates coins, only detecting gold rings and pull tabs? How is this done without the use of notch discrimination? A brain teaser for new and old metal detector users. The answers reveal a good lesson in proper metal detector and coil selection.

The Fisher ID Edge when put in Jewelry Mode only detects targets in 0 / +18 target ID range.

Here is the Target ID range for the Edge.

0--+8 = foil range
+9--+11 = Nickle range
+17--+18 = Square tabs/Brass range

In Jewelry Mode the below is rejected,
+20--+22 = Zinc Pennies
+28--+30 = copper pinnies and dimes
+30--+34 = Quarters
+34--+36 = Silver

And of course all signals on the minus side of 0 (iron) is also rejected.

But the Edge manual states that the factory presets are for beginners to just be able to use as a "Quick Start" turn on and go and many advance users would dig all good positive signals.

Mark

Other name branded detectors have "User Programmable" interfaces that can let a user pick and choose any combination of target responses they want to except or reject.
Now if a detector only has a discrimination control then its not possible to do outside of a notch system as you mentioned.

Mark

The Disc mode on the BH Time Ranger is essentially a notch system. Any one or all ID segments may be knocked out or the Blanker may be used as a Zap. Alternatively, you can "Sniff" a target and accept only it, rejecting everything else.

-Ed

Ground balance settings.

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Fisher F5 - Whites DFX / Bigfoot combo - Minelab Explorer SE Pro - ETPro - Tesoro Compadre

Ground Balance can be the culprit. Question that? Best not unless you know the specific detector make and model, and the person demonstrating that glitch.

I'd say the best example of the Ground Balance setting causing the high-conductive coin/target loss would be something like any of the Tesoro Bandido models, as well as most other manually GB'ed Tesoro's. Also, many of the factory preset models that have the internal GB trimmer set too high, or the models that have an even more annoying problem (like the Sidewinder µMAX, original Conquistador and a few more) that will shift the GB setting when you adjust the Discriminate level! Turn the Disc. too high and the GB is then adjusted way too high and a full-positive GB setting, or something close to that, will reject or ignore things like big silver dollars, often half-dollars, and in some cases even US quarters.

It related to how the Discriminate mode circuitry is tied in with, and affected by, the Ground Balance setting.

Then, as others stated, if a model features a full-range notch or segmented Discrimination, you can reject high conductors and still get a hit on the lower-reading targets.

Personally, I never use more discrimination than iron nail rejection unless it is absolutely necessary, and I always check and double check my Ground Balance setting. With the Gamma, Omega, G2 and T2, the automated GB is quick and easy, and you usually don't suffer the dilemma you mentioned.

Monte

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"Your Eyes, the ONLY 100% accurate form of Discrimination!"

Stinkwater Wells
Monte V. Berry Sr.
monte@stinkwaterwells.com
(503)481-8147
My main use favorites in order by brand:
White's
MXT Pro w/6½",
VX3 w/950
Tesoro
.. Replacement coming ..
Teknetics
Omega w/5½x9¾
G2 w/5" DD