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Steve Herschbach

Minelab Equinox Multi-IQ Technology Part 2

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From http://www.minelab.com/go-minelabbing/treasure-talk/equinox-technologies-part-2This is the second installment in a blog series introducing and explaining the technologies inside our new EQUINOX detectors… (Read Part 1 here.)

What actually is Multi-IQ technology? What does the name stand for? What frequencies does it use? Is “Multi” the same or different for the various Detecting Modes? Is Multi-IQ the same or different for EQUINOX 600 and EQUINOX 800? Why use a single frequency? How does EQUINOX perform in certain environments? How does EQUINOX perform compared to other Minelab detectors? How does EQUINOX perform against other brand detectors?

These are some of the myriad of questions we have seen since we published our EQUINOX Product Notice in mid-September. Some of the answers will have to wait until Minelab publishes reports from our field testers and/or you get your own hands on a detector to try yourself. In the meantime, let’s look further into the aspects of Multi-IQ technology.


Multi-IQ is derived from:

Simultaneous Multi-Frequency In-phase and Quadrature Synchronous Demodulation.

So, full marks to “Pimento” on the Thomas Dankowski Metal Detecting Forum for this great deduction:

 “I think the IQ part of Multi-IQ is not suggesting how Intelligent it is, but is alluding to the mathematical I and Q, representing the two quadrature (90 degrees apart) components of the signal, (which are then demodulated, a key part of most metal detector workings)”

But, that doesn’t mean EQUINOX is not an intelligent detector as well! We can go to a statement from Dr Philip Wahrlich, our principal technology physicist, about a key difference of Multi-IQ compared to the demodulation taking place in conventional single frequency VLF detectors:

“Within the Multi-IQ engine, the receiver is both phase-locked and amplitude-normalised to the transmitted magnetic field – rather than the electrical voltage driving the transmitted field. This field can be altered by the mineralisation in the soil (in both phase and amplitude), so if the receiver was only phased-locked to the driving voltage, this would result in inaccurate target IDs and a higher audible noise level. Locking the receiver to the actual transmitted field, across all frequencies simultaneously (by measuring the current through the coil) solves these issues, creating a very sensitive AND stable detector”

Precisely measuring these extremely small current variations is quite remarkable if you consider the levels involved. It’s actually parts per billion, or nanoamp signals, we are talking about here!

With Multi-IQ, we can derive much greater target ID accuracy and increased detecting performance, especially in ‘difficult’ ground. In ‘mild’ ground, single frequency may perform adequately, BUT depth and stable ID’s will be limited by ground noise; whereas the Multi-IQ simultaneous multi-frequency will achieve maximum depth with a very stable target signal. In ‘strong’ ground, single frequency will not be able to effectively separate the target signal, giving decreased results; whereas Multi-IQ will still detect at depth, losing a minimal amount of target accuracy.  This is how we would generally represent the multi-frequency advantage, based on our engineering test data.


 Let’s hear more from Philip Wahrlich about the technical details:

“For each frequency the detector transmits and receives there are two signals which can be extracted which we refer to as I and Q. The Q signal is most sensitive to targets, while the I signal is most sensitive to iron content. Traditional single-frequency metal detectors use the Q signal to detect targets, and then use the ratio of the I and Q signals to assess the characteristics of the target and assign a target ID. The problem with this approach is that the I signal is sensitive to the iron content of the soil. The target ID is always perturbed by the response from the soil, and as the signal from the target gets weaker, this perturbation becomes substantial. With some simplification here for brevity, if a detector transmits and receives on more than one frequency, it can ignore the soil sensitive I signals, and instead look at the multiple Q signals it receives in order to determine a target ID. That way, even for weak targets or highly mineralised soils, the target ID is far less perturbed by the response from the soil. This leads to very precise target IDs, both in mineralised soils and for targets at depth.


“How many simultaneous frequencies?” you may ask, wondering if this is a critical parameter. Minelab has been carrying out detailed investigations into this in recent years. Just as you can colour in a map with many colours, the minimum number to differentiate between adjacent countries is only 4 – a tough problem for mathematicians to prove, over many years. Similar to the map problem, it’s perhaps not the maximum number of frequencies needed to achieve an optimum result, but the minimum number that is more interesting. When it comes to frequencies in a detector, to cover all target types, how the frequencies are combined AND processed is now more important, with the latest detectors, than how many frequencies, for achieving even better results.

Efficient new technology = lower power = lighter weight = higher performance.

* 20 kHz and 40 kHz are not available as single operating frequencies in EQUINOX 600. The Multi-IQ frequency range shown applies to both EQUINOX 600 and 800. This diagram is representative only. Actual sensitivity levels will depend upon target types and sizes, ground conditions and detector settings.

The above diagram is intended to be a simplified representation of how different frequencies of operation are better suited to different target types; i.e. low frequencies (e.g. 5kHz) are more responsive to high conductors (e.g. large silver targets) and high frequencies (e.g. 40kHz) are more responsive to low conductors (e.g. small gold nuggets). The EQUINOX 600 offers a choice of 3 single frequencies and the EQUINOX 800 offers the choice of 5 single frequencies. Both models also have simultaneous multi-frequency options that cover a much broader range of targets than any one single frequency can – and they’re different across the Detecting Modes! 

We’ll consider this further in Part 3…

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On ‎10‎/‎31‎/‎2017 at 12:57 AM, Steve Herschbach said:




I would be interested to see this chart compared to other Multi-Freq machines such as the CTX.  My guess is the depth may be about the same, and the Target ID would be a bit better on the CTX.  But in an "under $1000" package... exciting.  Tim.

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Tim --

I would offer a counter-point.  I think target ID will be a little bit better on THIS unit (even better than FBS).  Obviously, this is all speculation, but from what I can gather, reading between the lines (while given my lack of electronics engineering knowledge), it sounds like one of the big improvements/technological advances that is Multi-IQ, as compared to prior multi-frequency technologies, is revealed in that first paragraph that Dr. Wahrlich is quoted.  While he gets into a bunch of stuff about phase- and amplitude-locking, drive voltage, etc. etc., my read on that, pondering it, and then putting it into a "conclusion" is as follows...

It would seem that apparently when prior multi-frequency units arrive at target ID, they are comparing receive waveform to an ASSUMED transmit waveform.  I say ASSUMED, because apparently a drive voltage is sent to the coil, and it is from this DRIVE VOLTAGE that the transmit waveform's "properties" are "assumed" (amplitude, phase, etc. etc.)  But, I can see where that would be "idealized," because ANYTHING between control box and coil that would alter that drive voltage, even SLIGHTLY, would result in a correspondingly, slightly different transmit waveform.  So, if, for illustration purposes, 1 volt is the "drive voltage" but only .99 volts is used at the coil to generate the transmit waveform, then the transmit waveform (resulting from the .99 volts) would be slightly different from a transmit waveform that would be generated by 1 volt.

AND SO, if all of your calculations of target ID, soil mineralization, etc. etc. are based on comparing a tiny, weak receive signal to an ASSUMED, IDEALIZED transmit waveform, but the transmit waveform the machine ACTUALLY produced (and to which the receive waveform SHOULD HAVE BEEN compared) is slightly different, I could see where this would introduce ID inaccuracy, etc.  And according to Dr. Wahrlich, THIS is apparently one of the advances that is going to show up in Multi-IQ -- that they are measuring the transmit voltage/waveform AT THE COIL, not at the control box, so the receive waveform to transmit waveform comparisons/calculations performed by the unit will be MORE ACCURATE than before, in prior technologies.

My conclusion -- if all of my understanding of the technical part of this is correct -- is this:

We all KNOW that multi-frequency technology is an improvement over single-frequency technology in terms of target ID; now, this new "breakthrough" that is part of Multi-IQ technology seems like it would mean that Multi-IQ technology is an improvement over prior MULTI-frequency technologies in terms of target ID.  

If my conclusion is correct, then we may all -- even users of FBS/FBS2 -- be in for a pleasant surprise.

(I might also note that improved ability to deal with soil mineralization and the associated positive effects on accurate target ID basically implies, for all intents and purposes, as a necessary side effect, improvement in depth capability as well....because after all, we know that deterioration of target detection ability with depth is largely due to the effects of soil mineralization "drowning out" the target signal; improving your ability to deal with soil, all else being equal, means an improvement in depth capability...hmm!)



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Steve, great comments and deductions.  I am all about receiving a pleasant surprise.  Your comments make perfect sense upon re-reading the original article.  For me the key is going to be how it manages the difficult mineralized ground that I live in - and how it feeds that information back to me, so I am very interested in your description of the wave form comparison between actual and assumed.  If this new technology can better sync the machine's language to match known target id's... you are correct, the result will be more accuracy in the field.  Of course the challenges are all the variables that can impact the waveform (as you outlined above) - and how the machine interprets those variables.   This is fascinating and exciting stuff!!  Tim.

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One thing about Minelab - when they introduce a complete new detector series it is usually in line with this statement "When Minelab develop a new detecting technology we aim to create a paradigm shift from existing products and provide a clear performance advantage for our customers."

Look at the history of multifrequency and selectable frequency at Minelab:

1991 BBS - Minelab Sovereign and derivatives like the Excalibur

1999 FBS - Minelab Explorer and derivative models like the E-TRAC

2005 VFLEX - X-Terra model series

2012 FBS2 - Minelab CTX 3030

2017 Multi-IQ - Equinox 600/800

I am a bit surprised that so many people consider BBS and FBS to be magical technology that can never be improved on. There are two obvious weaknesses, slow recovery speed/target masking and relative insensitivity to low conductors as compared to some competition. Multi-IQ is addressing these issues.

What then going forward? Will a CTX 4040 have FBS3? Personally it looks to me like BBS/FBS has hit the end of the road. Just like with the GPX 5000 where Minelab recognized they had milked PI for all it is worth, and moved on to the GPZ 7000 and ZVT technology. People worry about the Equinox eclipsing (Eclipse would have been a good alternative name to Equinox) the CTX 3030 when it looks to me more like Multi-IQ setting the stage for future developments. One thing the CTX platform does is allow for a much more powerful battery, and one can only imagine what Multi-IQ combined with a more powerful battery and tuned for high conductors would be able to do, while retaining the low conductor attributes of the Equinox. And while adding target trace, etc. to the mix.

Take the above with a grain of salt. I have no inside information about where the CTX platform is headed. These are just my speculations based on what I would do if I were laying out a product roadmap. Looks to me like Minelab has plenty of room to maneuver going forward. Equinox and Multi-IQ are probably just the start of what you will see coming from Minelab over the next decade. The CTX has been out over five years now and has had a good run, but there is no reason to think it can't be surpassed.

I am consolidating the Minelab Multi-IQ Technology Explained posts into a single document here as each installment is released.

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