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Discriminate on the GB2


wjbell

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Question about discriminate. Basically about the sounds it makes and if mines working right. Instead of trying to explain it on the board I just made a video of the question with a little test. If anyone can let me know what to listen for, if it's sounds like it's suppose to and why there's not that much difference between gold and iron.

Really appreciate it. Here's the video:

GB2 discrimination video

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Hi wjbell,

Yes, it sounds like your GB2 is working correctly. I am not sure what the manual says about the discriminate feature but to be able to give a good signal on small gold, the disc setting has to be quite critically set. This means it will be right at the edge of rejecting trash while detecting small gold. Trash on the GB 2 is simply types of ferrous (iron)junk.

As for non ferrous objects, all should sound good including foil, or the coins you tested. Since gold can vary in purity and size, it is necessary that all non ferrous objects give what is considered a good signal.

Don't expect the discrimination feature to tell you something about the metal other than whether it is ferrous or non ferrous and even then it can lie to you. Personally, I have yet to find a perfect discriminating detector and I have owned or at least tried a bunch of different detectors.

One other note about trying to discriminate iron junk and that is, the signal from iron objects varies depending upon the orientation, shape, etc. So, something like a bottle cap may be rejected most of the time, or maybe some of the time, but seldom all the time. Maybe one pass it might sound good but change the sweep rate and that response can change. Nails and other thicker ferrous metals may be rejected a little easier, but nothing is etched in stone.

What I am trying to day, is don't expect discrimination perfection because it will not be there on the GB 2 or any other VLF that I have tried. Fortunately, the disc feature does work well on the GB 2. At least, it does on mine and yours sounds like mine.

Reg

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Hi wjbell,

I am not sure what the manual says about the discriminate feature but to be able to give a good signal on small gold, the disc setting has to be quite critically set. This means it will be right at the edge of rejecting trash while detecting small gold.

Reg

Thanks Reg. I had a question about this. What do you mean critically set? Isn't it just a switch that you flip into discrimination mode? There's nothing to adjust the level of discrimination is there?

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Most detectors with a form of discrimination are used for coin hunting and as such have an adjustable discrimination control that can be set over a wide range depending upon just what a person wants to accept or reject.

On the GB 2, this control is internal and has to be set just to the point where very small gold will be accepted but most iron will still be rejected. If this control is not adjusted correctly, then it may be possible that some gold will be ignored or some iron may sound off good. So, the trick is to critically set the control to the right point.

Keep in mind that even a detector that is critically set can still detect some iron objects as good or maybe ignore certain gold nuggets. The reason is, there are too many variables that can influence just how an object appears to the detector. A good example is a gold nugget with a small amount of magnetite attached. Since magnetite is a very strong negative response, it doesn't take much to cause a good target to appear bad. Worse yet, lets say you are going to test your test nugget and you set that nugget on a rock containing concentrated magnetite. If that were to happen, then it is very possible the detector will fail to properly give a good response.

The point is, no discrimination feature is foolproof and when it fails to give an accurate indication, the result is usually one that causes a failure to detect a good object. On some detectors this is worse than on others. Even things such as signal strength of a good object when compared to the ground signal can influence just how accurate a discrimination feature is. In other words, a small nugget may respond correctly in an air test, but really bad ground may cause a rejection of that same target. This is quite common with many detectors I have tested.

One of the tests I used to try on different gold machines was to take a small nugget and place it next to a small magnetite rock and see how well that nugget can be detected. Fortunately, the GB 2 did quite well, especially when compared to some other detectors.

On some detectors even the ground balance adjustment can have a negative influence. So, it is always a good idea to make sure the detector be properly ground balanced when making the tests. This is why it is often stated that one should dig it all rather than try to use the disc feature to make the right determination. Unfortunately, some locations are so littered that the dig it all concept isn't practical or even logical. In such areas, then the disc feature can be a benefit. Just keep in mind that it is very possible one will ignore a desirable gold nugget and there is nothing wrong with the detector. In some cases when this happens, it may be about impossible especially for the less experienced operators to figure out why it happened. The natural tendency is to think there is something wrong with the detector. In most cases, this is not the case at all.

Finally, keep in mind that generally, using the discrimination feature will result is some depth loss. The mindset is to only give a good response when the detector knows or thinks it knows the target is a good object. If the signal is just a little to weak to make a positive evaluation, then the object is ignored. Since this usually happens without the operator's knowledge, the detector appears to be working fine and detecting all gold. So, just remember that usually, using the disc feature will result in some depth loss.

Reg

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