Large silver coin not detected

[all iron]

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.

 

[MarkCZ]

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

 

[MarkCZ]

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

 

[Ed in SoDak]

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

 

[Mike Hillis]

Ground balance settings.

 

[Monte]

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