Minelab H1-24 Results

[jasong]

57 minutes ago, Digalicious said:

Jason,

Multi core / thread processors are pretty cheap. Even fairly basic CPUs in computers have the computational "power" to easily run tasks, that are far more complex and resource hungry than what a metal detector needs.

If all it takes to get much better performance out of a metal detector, is to add $200 to the price to get a "better" processor, wouldn't the engineers have done that by now?

In addition, I'm not so sure about your EMI suggestion. I mean, the bottom line is that a metal detector doesn't know if the signal it receives is coming from EMI or metal in the ground. As such, there is no viable way to mitigate EMI in SMF modes, without losing performance in one way or another. Channel hopping with tiny 0.2 khz increments, isn't going to mitigate EMI, given that the EMI and its harmonics are wideband, and so is the receiver (SMF).

I'm not talking about throwing more power at obsolete design paradigms. I'm talking about adapting new design principals to the power we available today. Until very recently, most detectors were still designed like it was 1995, even when they did use more modern components. Like procedural style programming instead of object oriented. One thing at a time type stuff, it's ultra inefficient. Throwing more processing power at old designs and ideas accomplishes little and is not what I'm suggesting. 

EMI is absolutely something that can be dealt with more effectively. It's done already in scientific instrumentation via numerous different methods, though these are complex. I suggested one simple way that I know already works in electronics other than detectors - real time noise monitoring and channel selection. That alone would save the 30 seconds of noise cancelling plus would keep you on average on a much quieter channel. 

I'm just repeating myself here though. I guess people either understand what I'm saying or not. 

 

[jasong]

16 minutes ago, phrunt said:

EMI is a tricky one to overcome, as the detector can't tell EMI from signals, maybe it could use processing power to check for patterns and try filter it out, but then you're adding another pretty risky filter.  Better shielding on the detector itself can help, and that's an area Minelab for some reason is a bit lacking, so they could get minor improvements there.

Right, this is one commonly used method in instrumentation. I've posted about this years ago, but the way it's done is by doing something like a gradiometric analysis. In other words - you sense noise from two different spots in real time, and then look at the rate of change and direction when possible of the E field. Vector gradient analysis. (fancy terms for looking at rates of change and direction)

The difference between the signal from the ground to the coil is much higher than the difference between taking that same reading somewhere else, say the control box.

Now the same analysis can be applied to EMI. Since it originates from the sun, lightning, planes, cell towers, etc the difference in magnitude is far less as it's picked up between those same two points. So you can more easily determine those types of signals are likely to be EMI. Now - with enough CPU speed you can do further analysis on the signals to differentiate them, and still have results in "real time" before the brain hears anything like Fourier analysis on top of the gradiometry. You can even take gradiometry further and do vector (directional) analysis with a fast enough CPU and some clever circuitry to determine which direction the signal is coming from.

This is a massive oversimplification but I'm trying to keep it understandable for all.

[phrunt]

The control box intentionally picking up EMI to be used as an indication of coil EMI sounds plausible, as the control box isn't going to be picking up the in-ground targets so some sort of antenna with a role of picking up EMI signals and using that to help cancel them out.

[jasong]

There are a ton of different ways that could be implemented now that we have the processing power to do them. A lot of this stuff was techniques that were well known in the 90's because it's what we had to do to adapt lab equipment and tools to specific uses in school. 

A bunch of ideas probably wouldn't work. I probably misunderstand others. That's science and engineering - experiment and try. But I've seen enough in other products and instruments to be pretty comfortable saying that I really don't think detectors are seriously using the power we have available cheaply today.

But again, this is stuff I see greatly benefiting exploration prospecting. Stuff that speeds up ground coverage, saves time. Not as beneficial for flogging old patches type detecting where one is already going slow, and a slow/noisy rig doesn't matter as much.  

In terms of raw power for getting every last deeper crumb out of an old patch, it's going to be hard to be beat an old GPZ with a larger CC X Coil, I agree there. These changes will be smaller advantages for that type of work. That rig is also a poor exploration machine though. 

[Dug D]

I think a big step forward would be a detector circuit that only detects aluminum and indicated that on the screen, sort of like how detectors treat iron/red numbers. Imagine if the Manticore had a range where aluminum appeared like the iron does top and bottom of the screen or yellow numbers. 

[Past Member]

 

4 minutes ago, jasong said:

The difference between the signal from the ground to the coil is much higher than the difference between taking that same reading somewhere else, say the control box.

Now the same analysis can be applied to EMI. Since it originates from the sun, lightning, planes, cell towers, etc the difference in magnitude is far less as it's picked up between those same two points. So you can more easily determine those types of signals are likely to be EMI. Now - with enough CPU speed you can do further analysis on the signals to differentiate them, and still have results in "real time" before the brain hears anything like Fourier analysis on top of the gradiometry.

This is a massive oversimplification but I'm trying to keep it understandable for all.

Well Jason, I'm glad you're trying to make it understandable for all, but I still don't understand what you're trying to say ?

For example, what does the control box have to do with EMI, given that the control box components can be easily, and effectively shielded?

In addition, EMI is hitting the coil at random intervals, frequencies, and harmonics, so I don't see how any kind of timing or analysis can differentiate between that, and the random signals from metal in the ground.

Granted, we know that EMI typically produces signals that are weaker than most coin sized objects in the ground, which is why reducing the sensitivity, effectively reduces EMI, along with losing good targets. We also know that most EMI produces TIDs that range from ferrous to just under zinc. Which is why discriminating out everything below zinc, when cherry picking high conductors, gives the illusion that EMI has been mitigated.

I suspect that EMI and its relation to SMF has been a thorn in the side of engineers for a good 20 years, yet EMI is still a major problem. There's just no way to eliminate random EMI signals in SMF, without also eliminating a lot of good signals. In other words, true EMI mitigation, would be akin to "throwing out the baby with the bath water". 20 years of metal detector engineers working on the problem, seem to agree.

[Past Member]

1 hour ago, Dug D said:

I think a big step forward would be a detector circuit that only detects aluminum and indicated that on the screen, sort of like how detectors treat iron/red numbers. Imagine if the Manticore had a range where aluminum appeared like the iron does top and bottom of the screen or yellow numbers. 

Ya, that's one of the Holy Grails of metal detecting. With a detector like that, one could repeatedly hunt a beach, park, sports field, etc, and walk out with a handful of various gold jewelry. I'd pay an exorbitant amount of money for that detector. One hunter said he would remortgage his house to buy a detector that could distinguish between gold jewelry and aluminum ?

Too bad that distinguishing is not possible with an induction balance metal detector.

[VicR]

Maybe the next gold detector from Minelab will not be able detect deeper but will be able to more clearly identify and amplify the faint signals that we miss - refer to a Bruce Candy / Minelab recently approved Australian patent 2023202011.  The abstract of the patent reads -

A method for detecting a target using a metal detector by producing at least two different modulated
audio tones, by modulating a first audio tone with a first stereo audio modulator signal and modulating
a second audio tone with a second stereo audio modulator signal; and applying at least the first audio
tone to a left side of an audio stereo target indicator indicative of the target, and applying at least the
second audio tone to a right side of the audio stereo target indicator; wherein the modulating of the
first audio tone and modulating of the second audio tone, comprises one or more of the following; a
modulation of a volume of a tone, a modulation of a pitch of a tone, a modulation of relative
harmonics ratios of a tone, a modulation of a chord richness of a tone.

I have never thought about this before but i am assuming that the current signals we hear from detectors are in mono - the same sound in left and right of the headphones. Having stereo signals may give the engineers more scope to amplify the signals we want to hear.

[phrunt]

I wonder if he's moved onto helping with the Coin and jewellery detectors more so than the gold detectors, seeing they've already indicated multiple times in various investor documents that's an area they're applying more focus now.