Geotech

There should be no diode. Some coils may have a thermistor but that's not the problem. The 4x6 is a DD coil that is completely encased in epoxy. DD coils are incredibly sensitive to coil movement (concentrics are not) and any movement of the epoxy will knock the coil out of null and cause overload. White's had fits with those coils in production, after the epoxy was poured it was baked in an oven for 2-3 days, then sat for a few weeks to fully cure. Then the final tweak null was applied and the coil was sealed. Sometimes even that wasn't enough and coils would drift months later.

You have two solutions. 1) Don't run it at max sensitivity. 2) Remove the bottom plastic and re-null the coil. For #2 there is a loose winding that is held down with hot-melt. Moving that wire around will alter the null. To do it right you need an oscilloscope, but you might be able to at least make it better by using a ferrite and the detector's overload audio.

Carl from White's here...

7 hours ago, Jason-NEK said:

Last year Minelab dropped their patent rights on their multi frequency technology and companies like Nokta Makro have started to utilize the techniques of Minelab into their new, supposedly first true, simultaneous multi-frequency machine the Legend.

Patents normally expire 20 years after first filing, so their '360 patent (BBS/FBS) expired over 4 yrs ago. I've seen nothing from NM or XP that looks anything like the old ML sequential multifrequency. But they do look like the Equinox's simultaneous multifrequency, which first showed up in the White's DFX. In fact, one of the MF modes on the Deus 2 has the same waveform as the DFX. That's not a surprise, it's just how you do a 5th harmonic system.

It's always a challenge to take over someone else's code. And the V3 code is probably one of the largest and most complex detector programs ever written. To make things worse, the processor is obsolete so, at a minimum, it needs to be ported to a new processor. To make things downright miserable, the V3 had some particular problems that would need fixing, some in software but also in the circuit design. The people who designed the circuitry and wrote the code know where the rocks are. Garrett will have to figure it out, could take a while. Probably faster to start with the Ace Apex.

Yeah, V3 is still one of my favorites. The SpectraGraph display has still not been equaled, or even approached. It's a shame it ended up a dead end.

He's working on a utility pipe tracer. Unfortunately the work we did at White's holds no water here. White's is viewed as a failed company with failed products.

On the V3, it was written in C++. It would be a difficult challenge for someone to take on that code other than the guy who wrote it, who now works for FTP. Also, the V3 was not a depth demon and had some issues, notably with ground tracking. And recovery speed was average. It would need a complete hardware re-design and a lot of software overhaul. Apex might be a better starting point.

On Minelab, the rumor I've heard is that the Equinox 1000 is getting close. It is not an enhanced Eq800 but has a new mechanicals with a larger pod.

12 hours ago, Cal_Cobra said:

Carl is there anything on the circuit board Simon shared that you find particularly interesting, or is it just status quo as expected?

Hard to say with just photos. I'm not seeing any signs of hardware demods so it appears to be direct sampling. That's slightly surprising, but maybe NM cracked that nut with the Simplex, I don't know.

23 hours ago, Cal_Cobra said:

If it's that, it's not going to set the world on fire, but still that's more than enough compute power for a metal detector.  Could always leverage a DSP if needed if not already.

32b Cortex processors have plenty of horsepower for detectors. M4 cores (as apparently in the Legend) have a hardware multiply so they even have some DSP muscle. Almost all my designs use STM32 micros. The F-Pulse/TekPoint has an STM32L072, the walk-thru has an STM32L496, and another design has an STM32F767.

4 hours ago, phrunt said:

it's interesting they didn't go with Bluetooth 5.2 with the LC3 codec where the latency is as low as 5ms.

Have you seen anything with 5.2 LE audio? I think Qualcomm has a chip that supports it and I've seen one set of 5.2-LE earbuds, but nothing else. No off-the-shelf headphones or transmitters. The companies I'm watching in particular are ST-Micro and Nordic, because working with Qualcomm is a royal pain. We also tried Feasycom and found them to be very unresponsive.

5 hours ago, alan46 said:

also, does the pulse power also affects the depth, i guess from the small battery and the advertised 14 hour life that it is using less power per pulse, if power maters then will using a 20% lower resistance for the new large coil (thinner wire) help force a bigger current and consequently more power (assuming it is driven by a voltage generator)?

No, lower coil resistance won't help (and that would require thicker wire, not thinner). PI pinpointers are not designed to go deep and are more concerned with battery life so the pulse timing would likely need to be changed, as would the power supply that drives the coil. And because raw depth is not critical the RX circuitry is probably pretty skimpy and would need redesigning. In short, you need a different PI circuit.

Quote

note: I know i can find many similar models with big coils but for some reasons am limited to this particular detector and I want it to find gold jars 3 foots in mineralized ground

This circuit isn't going to do that.

31 minutes ago, bklein said:

What is he coating the coils with before they go into the oven and why doesn’t it stick to the wood?  Where does he get the coil forms? Is there a trick to get an English translation?

Probably he's using bondable magnet wire which just requires alcohol to activate. Then you want to bake it at ~150°F for maybe an hour to outgas the alcohol. I rub Johnson wax on my coil forms to keep the coils from sticking.

Selling into big-box stores is a challenge. It's easy to think that, say, a Simplex could move into that market and kill our sales but there is a lot more to it than just the detector. You need a business infrastructure that can deal with the demands of on-line & big-box venues. For example, FTP can receive an order for 1000 detectors in the morning and build them all from scratch and ship them by that afternoon. Can't ship same day? Then the order is canceled. And when Stuff-Mart wants to return 5000 unsold detectors that are still brand new but the boxes are beat up you have to accommodate that if you ever want to do business with them again. White's tried to do this in their waning years but was unable. Garrett does pretty well at the game, Minelab less so. It really demands a large domestic presence and having the factories and warehousing here is a huge benefit.

As I mentioned in another thread, contract manufacturing is not FTP's primary business. It is slowly growing, but metal detectors pay the bills.

When you subtract the frequencies for salt cancel you end up with a composite signal that is used for raw detection. Yes, this signal will be less sensitive to target near the salt notch.

The CZX was not an updated CZ, it was a completely new design. It was specifically designed for prospecting and that's where it failed. I tried to get people to shift the project to coin/relic/beach but was unsuccessful.

FTP does contract manufacturing at the Juarez facility but metal detectors are still the primary business.

5 minutes ago, Dan Fox said:

So are you saying for subtraction modes the high frequency is only really used for salt identification within the algorithm?

No, it's also used for target detection & ID.

From his comment I'd say Luis wasn't involved in the test, he only posted it. I think this was a recent outing by Alexandre to evaluate some design changes. I have no info on whether the AQ will get back to production; my vote is 'no' unless the pod is redesigned.

The AQ is a really good design (circuit-wise) and should be able to beat the new MF designs in depth. I agree that the iron masking works well with isolated targets but in heavy iron it struggles. I hunted around fire pits on an Oregon beach and the cheeps and chirps that get through the audio make it a real chore to use. In fairness, many VLFs tend to do the same. It's a shame this was pitched as "discrimination" or "iron ID" or "tone ID" etc etc. I wish we had seriously undersold this feature and let people figure out its value. It is useful in some situations.

Wind a coil of wire and then "short" it with a resistor. This allows you to accurately make any tau you want. For salt you want a really low tau which allows for a fairly high R. So start with a small gauge wire, something small enough it is not detected alone, maybe 30awg. I would start with 5-6 turns @ 3-4" diameter. Then use a pot as the R-element and adjust the pot until you get the tau you want. Measure the pot, replace with a fixed resistor.

If you don't know the tau you're shooting for then make a guess and wave in front of the detector (assuming MF with salt notch enabled). When you get it right the detector should have no response. BTW, the pot/resistor needs to be mounted well away from the coil. Extend the coil wires 12" or so down a handle and put them at the end of the handle. Make sure the wires down the handle are twisted pair.

I have no idea. If it were my design then only beach modes would do salt subtraction by default, although I might include the option in other modes as highly alkaline soil can also be a problem. Maybe that's what Deus 2 is doing. I may get the chance to borrow one, if I do then I'll make a salt wand for it and test it.

Frequency subtraction is how salt notching works in an MF design. Salt has a weaker response at low frequency and stronger at high. So if you subtract them in the right proportions then salt disappears. In older MF detectors this was done all the time. The V3 gave the option of turning it off because it also notches out really small gold. I assume newer models only subtract salt in the beach modes. If there is no salt then it's also possible to add frequency components which (I think) will improve the resistive response across the board, which is the signal used for determining the presence of a target.

No, targets with identical taus will have identical VDIs. Phase is arctan(2π*f*tau) and VDI is a translation of phase angle.

No, by the time the headphones were released the Cypress module we used was heading toward end-of-life. Plus, that module wasn't a good choice for making a plug-in adapter. The intent was to design a whole new wireless system but that never happened.

4 hours ago, GB_Amateur said:

Possibly I'm assigning a conductive explanation to a ferromagnetic property....

Yes, that's a magnetic response, not an eddy response.

28 minutes ago, GB_Amateur said:

I'm surprised you were able to get so many different alloys to create this plot.  Did you mix them yourself?

What I've never seen is a similar plot for copper-silver alloys.  You wouldn't happen to have that one?

Data came from the CRC Handbook of Chemistry & Physics. I've looked all over for similar data for copper-silver alloys but haven't found any.

12 hours ago, Cascade Steven said:

Geotech:  I've been away from the forum for a while and just dropped in on this very interesting conversation.  I have a question about conductivity and apologize in advanced if I missed the answer elsewhere.  When you talk about conductivity of metals, do you refer to electrical conductivity or magnetic conductivity as in magnetic susceptibility?  Thanks

What Pimento said. All we're talking about here are eddy current responses which depend on electrical conductivity. Magnetic responses (soil & iron) involve susceptibility and BH curve hysteresis. Most iron also have eddy responses which complicate things even more.