ML EQUINOX coil discussion thread

[EL NINO]

I got another good knowledge about Equinox coils .... in the new Black Sand box I mixed 3x more magnetite = 12% magnetite than in the first test box ... Tests are done at 10 cm depth of Black sand ..
The first tests showed:


1. Test result ... small 6 "coil at multifrequency ... / except Beach programs / no longer manages such mineralization and ... overloading ... secret weapons are here working at 1F at 5kzh, 10khz, 15khz, 20khz. ..by me there is a lower Tx performance so the received signal for the coil is still at an acceptable level ..
But don't expect much deep reach ... Detection of tested coin size targets is impossible through 10cm black sand ..


2. Surprise ... is of 11 "standard Equinox coil works well ,, and detects even at multi-frequency without problems coin size targets ...- but 12% magnetite mineralization no longer breaks strength and accuracy of multi-IQ ID .. showing ID is more like a classic Vlf detector ... shows higher and high ID numbers ...
In previous tests on 4.4% Magnetite mineralization, the strength of Multi-IQ ID is still maintained.


I think after these tests I get closer to the definition of how big should be the optimal coil for VLF or Multifrequency detector ... according to me it can be coil size from 8 -9""to 11" ..

[EL NINO]

It seems to me that Equinox is now more sensitive (less filters) to low-frequency signals - this is the ground signal area and the area of large metal objects.
Theoretically, this would also have an impact on better detection of high-conductivity large silver objects and the like.
Even a simple Airtest with a large silver with a dongle and no dongle on various recovery speeds could confirm that ..

[nordic]

Pulled good few smaller and bigger items today from one of fields. Did really well compared to my friends Deus, pretty much 1:2 in finds, perhaps luck or maybe not. Run full throttle sens 25, no bother at all - totally quiet off the ground. All targets were coming really clean. There was not one situation of an iffy signal without an ID, where I had to go over and over the target pressing coil down. Anything audible had an ID, which coincides with my findings in air tests. Field, however, had a lot of coke and iron too, but no problem with discrimination, not sure about unmasking, but pulled few small item from considerable depth, some took a while to pinpoint with external PP.

One thing noticed, that MD became very sensitive to larger metal objects, passing near fences or concrete armature bridges was giving long flutey sound, that I only ever heard when running recovery 1-2. But I was on 4. Also having a coil on the ground for 10 seconds or so, and then taking it away sounded this flutey as well, but not as prolonged as in mentioned earlier. Very interesting sensation of this coil "stickiness" to the ground.

Anyway, more testing some time soon. The dongle stays.

[nordic]

Most of my tests are around the detection threshold - the goal is to be able to sniff out smallest and deepest of things, to me anyway - if it can do that, it can do larger stuff too. Having such RX gain in the coil circuit and also gain in the digital domain (I think it is PCM1861 ADC), one of keys is clean power lines to lower the noise floor as much as possible to both the analog and digital sections. I think that ML could've used a better cable for the coil. The ADC setup in the control box looks minimal - looks like they run both analog and digital sections of the ADC from the same rail. I almost wish I could open the control box, but then knowing myself I would never end tinkering with it.

For the EMI, I think most of it is introduced through the coil... In all fairness, ML made Nox a very sensitive machine, because it reacts to any rapid changes of even a smallest magnitude, so any conditioning of the signal I tried so far only degraded the discrimination ability. I consider myself lucky to be able to hunt places where I can run the Nox at full or near full sensitivity, while some fellow users can't even go over 2/3.

[EL NINO]

Thank you Nordic


One possibility may be a test on buried objects on the boundary of the Equinox range. This allows you to quickly determine if a given power adjustment allows you to improve the depth of detection or better-accurate ID ...
Another good test could be the reach in Emi ...- where it would be found to work as such in an environment of electronic interference.

[nordic]

Hi EL NINO. I definitely see some improvement in target recognition after regulating the coil supply. I used soic ADM7150 for 3.3 Vdc. It doesn't feel going deeper, but TID does come more precise and stronger. Not a day and night, but noticeable improvement. I think it gives an extra sensitivity point+, in other words, for example, if I set sensitivity to 20 and can hear audibly a coin under the coil from a measured distance, but no ID, with the dongle, it does get the ID.

It happened I have bucket of sand, that I use for some cement jobbies around home, it is heavily mineralized as well, GB comes at around 60-70 over it. I did bury children's gold/silver ring about 10cm into it + it has another 10cm air gap, it was picking it rather nicely. I did similar tests before and that sand would just hide things and only give negative grunt, unless they are right on the surface.

I've read some minelab white papers, they claim, that beside the user sensitivity setting, they also do one in software in background, which, kinda, makes my tests, or anyone's tests in fact, a little invalid. They don't say however if they do so at startup only, or all the time.

Unfortunately I don't have any gold pieces to test, only few silver coins and gold rings. My floor at home is nails infested and pretty much gives iron grunt everywhere I move the coil. I find that with the dongle it seems to discriminate good items on it a bit better, or from further distance. I have a pistol ball lead bullet, about 5mm in diameter, with which the 11" coil always struggles at any distance - could never see it on the floor, but with the dongle I does come through in one direction. So something is working a tad better.

I do have all 3 coils as well, but for the sake of consistency I'm taking the stock 11" coil this weekend, and will report back if of any interest. The difficulty here is that these hunts are very subjective, but I'll be keeping the dongle permanently, I like it. Nox is less erratic with it. Have modified it heavily yesterday for more permanent setup, using proper gauge wires and shielding for different types of signals.

[EL NINO]

Nordick ... my view is to improve signal parameters - and signal / noise .. will still contribute to better detection .. Interestingly, it will be tested on ground tests ... - which can confirm the virtually the benefit of this improvement.
I would be especially interested in the result of this improvement on better work ID in Allmetal mode..on horseshoe..where in tests for 1 gram gold 24k brick at a depth of 16cm -in heavily mineralized "Black sand" I get mostly signal from negative -9, -8ID ... with occasional corect -management+ ID ... In discrimination mode by using discrimination to adjust detection to correct positive and accurate response of Tone and ID ..

I tested all 3 coil dimensions 6 ", 11", 12x15 " coils into Equinox .., big 12x15" coil gave the best response in Allmetal..as much less positive ID- I think it is somewhat better reach this coil - stronger received signal.

The test results confirmed that the appropriate coil size is superior and contributes to the depth of detection.
Even in heavily mineralized soil ... standard 11 "and large 12x15" coil proved well to detect 1gram of gold brick at 16cm depth in "black-sand" = 4% magnetite ..
The small 6 "coil was beyond the depth of detection ... and could not detect 1g of gold brick ... at a depth of 16cm ..

[nordic]

So, I have made this ugly little thingy running off the 9V battery through a 3.3v regulator, using an etched pcb from another project. The ripple in the Vdc line is now completely gone. There is HF noise present, but it is present even when the MD is turned off.
I can't tell if this made any different in air tests, so will have to take it out for field testing, it didn't make it worse sure.
In air tests, generally, filtering the Vdc seems to improve TID recognition - it comes a little sooner and is more consistent from extreme distance. I don't think it improved any air test depth, nothing obvious anyway. But if TID comes stronger, it can't be bad.
Was it worth the effort, maybe, I enjoy this stuff. Gave me a good deal of information on how parts of this stuff work.

[nordic]

Sorry Skippy, my bad, it was last year I had to cough up those as well - curiosity took over.

My plan is power up the coil amp with the battery through a low noise vreg. Separate to the control box. It is probably an overkill, but I want to see what it will result in.

[Skippy]

For connector, as you may know already, just look for "M12-8" or "M12 8 pin"
Did you miss my first post?

I just didn't want to spent 15+ Pounds on two connectors until I was sure I would need them. My broken coil already cost too much, no thanks to customs charges and related fees ... the coil cost me 20 US Dollars, I had to cough up 19 Dollars in fees to get it into the UK, plus the expensive international postage charges. Made me mad, partly with myself for not reading all the pages of detailed stuff on the UK government website about charges, plus Royal Mail taking a big cut...sheesh.

[nordic]

Exactly my findings as well, thanks for clarifying and confirming Skippy. As you have mentioned earlier, the RX signal is biased to about 1.6V via a divider, however a very close large object near the coil will clip the TX signal, I think this is where you see a triangle warning on the equinox as I found out by accident placing the MD on the metal sheet.

Equinox software appears to be looking for changes in the TX signal, so it doesn't really care if there is little TX signal present on the RX as long as it is constant and low enough. Anything not constant, like Vdc noise would have an adverse effect to sensitivity, if I understand it correctly. Same reason why coil needs to be moved over targets and does not work stationary, as it needs changes.

For connector, as you may know already, just look for "M12-8" or "M12 8 pin", but they are quite expensive I have to say...

When I put some filtering on the Vdc, I'm not sure which part it made "better", the power line in the control box or coil circuitry, but brought it down to about 20mV Vpp at the connector. There is background noise and also TX spikes present in it.

[EL NINO]

Mr. Skippy ... all your thoughts are right ..


If the coil balance is within proper manufacturing tolerances, such coil will correctly detect ...


dangerously if the coil is beyond the manufacturing tolerance of the balance.


I agree with the elimination of the Factor Emi I consider the essential element in better detection.

[Skippy]

The thing that newbies don't understand about coil nulling is this:
*If the coil is adequately nulled, the detector performs correctly.
*If the coil is super-precisely nulled, the detector performs correctly.
*If the null is beyond some limit, performance is degraded. Typically this would mean the ability to cope with ground that gave a strong signal would degrade, but strong target overload could happen, too. Depending on the detector, sensitivity will drop off, and ultimately fall to near zero.

I have some plans to try out some power line noise filtering, hopefully out in the field, though my break-in cable is a bit fragile .... may need to splash out on a proper free-socket.

[EL NINO]

Balanced 13 "ultimate works well on the Spectra .. because the Spectra V3's depth and sensitivity depend on the RX gain adjustment level ..- especially in light terrain ..


Equinox has no intrinsic coil diagnostics function ... like Spectra V3, it doesn't even have overload- / except for Beach 1, and Beach2, overloading down its Tx / .... to tell us that the coil may be outside its tolerance ..


According to Equinox, it processes the Rx signal at various gain levels - and therefore does not overload .. even with relatively large metal objects.
The electronics in the coil can do a good part of this work - and if the coil is within the manufacturing tolerance of the balance .. it will work fine according to me ..




Practical tests that I did on 7bar Fe3o4 Black sand -4.4% magnetite - where Equinox worked at almost full sensitivity - sensitivity24 ... tell me that Equinox has a different signal processing RX than usual for VLF detectors ..- Equnox rather, it is governed by a separate RX gain setting (automatically-or implemented in a given recovery speed) and also by a separate sensitivity-user setting


NORDIC .... Of course, I consider your effort to better tune the Equinox coil as a very good step that can improve the detector's performance ... and I'm waiting for your next results ...

[nordic]

Thanks EL NINO. Did you notice any improvement in MD operation? I did not really. However if I make nulling twice as bad using same technique, there is a drop in detection depth.

There is a noticeable change to a positive side if to tackle the noise in the Vdc rail, because by default the line appears to be quite noisy. It is also not exactly 3.3V, wonder if it is regulated sufficiently. With all the gain in the coil and the digital domain, that can't be good. I would expect the ADC analog section to be fed with the same line and it does not add anything good to SNR figures.

After applying some simple filtering techniques, I have noticed increased sensitivity to small things in front of the coil. Before, it would simply not react to them. In the field testing, the iron became identifiable clearer somehow, and generally MD was running quieter on max 25 sens.

Just a pic of it covered from the rain, sitting between the coil and the unit.


If to look at the TX coil firing timing, there is significant jitter present, but I'm not sure if it is a problem or not. My assumption the timing is controlled from the software causing such irregularities.