What Is The Technical Difference Between Discrimination And Notch?

[Chase Goldman]

51 minutes ago, Steve Herschbach said:

I'm a fairly proficient cherry picker with a PI detector just by reading the tonal responses. IAR is a way to try and replicate in electronics what a person like me is doing with their ears. Most round targets and most non-ferrous targets produce different signals than most ferrous targets. Not all by a long shot, but enough to sway the odds in your favor.

Exactly.  To piggy back on this; non-ferrous, symmetric targets at depth usually (but there are always exceptions) change tonal pitch in a smooth manner whereas small and large non-ferrous change pitch in a more abrupt or "unstable" manner even if the pitch change amplitude is the same.  A smooth valley or hill vs. a more abrupt pit or pinnacle.  That is our brains interpreting the different time varying pitch and amplitude changes and rates.  Using the Axiom which uses "on demand" ferrous checks vs. continuous ferrous blanking.  I can pretty much tell by the abruptness of the target signal audio changes in pitch and volume amplitude whether I am likely over ferrous and engaging the ferrous check just sort of provides a confirmation.  Then I still need to make a dig decision because none of this is 100% foolproof and factors such as the local junk you have previously dug, the junk density factor, your fatigue factor, and hunches that will come into play.  This is all integrated in your head in real time, and if you have done it long it enough it becomes second nature without you realizing you are doing it.  You just do it.

[Geotech]

5 hours ago, iron_buzz said:

I have wondered it it would also be possible to apply that same logic to non-ferrous targets for detecting in places where you want to ignore shallow coins and pulltabs and such so you can focus on the deep targets.

This is called "surface blanking." It has been featured on a few detectors but I don't recall the specific models. Garrett did it years ago, and I think either Compass or Discovery as well.

[Steve Herschbach]

I wish surface balancing had not been abandoned as a concept. Hey, there is a “new” control somebody can add to the next Pro Plus model. 

[Geotech]

1 hour ago, Steve Herschbach said:

As one of those old timers let me clarify that. It is not so much depth that is limited but the ability to detect the target, which can be perceived as the same thing.

All true. What I was talking about was the problem of old analog discriminators. Where setting the discriminator to reject pull tabs might reduce the depth on silver quarters by half even though they are no where close to the disc cut-off. It was well-known back then that to maximize depth, turn the disc as low as possible.

Digital designs don't have that problem, but they do have the problem you bring up. Every disc or notch setting can have (and probably does have) a "brick wall" cut-off. With digital discrimination it's a none-or-all situation, unlike analog disc where it's a none-or-a-lot-less situation. With digital disc, a bad target right on the edge of the disc setting will get broken up, but so will a good target just on the other side of the edge.

Like you, I prefer to use no disc and listen to tones. I also prefer mixed-mode where I can hear the AM signal at the same time. Makes for busy audio but you get used to it, and I think it is actually easier to listen to than a bunch of broken up crackling made by a digital discriminator.

[Steve Herschbach]

Two thumbs up for mixed mode and tones only! I guess it comes down to the difference between those that see the audio feedback as noise and those of us who hear the machine talking to us. I hate gagging my little buddy since he might not tell me something I want to know. 

The Excalibur was deadly because it had no meter and so forced the user to learn full tone detecting. The 17 tones soon meld into a few, with that sweet jewelry tone stopping the experienced hunters up short. Unfortunately it and its users were too good, and they cleaned out a lot of what was out there before it came along.

[iron_buzz]

8 hours ago, Geotech said:

This is called "surface blanking." It has been featured on a few detectors but I don't recall the specific models. Garrett did it years ago, and I think either Compass or Discovery as well.

I guess it didn't work out to well, then.

[iron_buzz]

8 hours ago, Steve Herschbach said:

Two thumbs up for mixed mode and tones only! I guess it comes down to the difference between those that see the audio feedback as noise and those of us who hear the machine talking to us. I hate gagging my little buddy since he might not tell me something I want to know. 

The Excalibur was deadly because it had no meter and so forced the user to learn full tone detecting. The 17 tones soon meld into a few, with that sweet jewelry tone stopping the experienced hunters up short. Unfortunately it and its users were too good, and they cleaned out a lot of what was out there before it came along.

I had a Manticore... for about a month.  I've owned a Deus for 7 seasons now, and found that with the Manticore, I was constantly checking the screen to read the TID.  About the only time I check the screen on the Deus is when I already know that I've got a pretty good target. 

It dawned on me the other day that the Deus audio is almost like tapping drywall to locate the studs... you can hear the tinniness of aluminum vs the solidness of a nice, thick brass artifact.  I did not have that with the Manticore.  I sold it.

[Sinclair]

I've used the Nox for 5 seasons and when I got the the Deus 2, I felt it sounded like crap ?
It's very likely a "got used to" thing. It takes some time to learn the machine's "language". On some machines a lot can be done with settings - so my Deus now sounds very "Minelabbish".. ?

[Lodge Scent]

VERY informative post! I appreciate all of you experts sharing your knowledge.