Whats In Your Coil?

[Geotech]

Twisting a pair of wires does cancel external EMI, it also cancels the outgoing magnetic field. In this case the leads are a very tiny part of a large coil which is highly susceptible to EMI and also generates a large magnetic field, so I doubt whether the wires are twisted or not makes any difference whatsoever.

Induced EMI is proportional to the area-turns (area of the coil times the number of turns of wire) which likely favors the small coil.

[Chase Goldman]

Would really like to see an X-ray of a Minelab Go Find coil, because externally it looks like a mono coil which is weird for an induction balance detector which uses a CW transmission coil and separate receive coil in either DD or coaxial configurations.

[phrunt]

30 minutes ago, Chase Goldman said:

Would really like to see an X-ray of a Minelab Go Find coil, because externally it looks like a mono coil which is weird for an induction balance detector which uses a CW transmission coil and separate receive coil in either DD or coaxial configurations.

In early specifications of the Go-Find 20,40,60 models they called it a mono coil, now they just say coil on the current specifications.  It is a mono coil.  The Ukranians some time ago from MarsMD modded a Go-Find to take coils and made a Mars Tiger work on it, I wish mine had a Tiger on it 🙂

Another coil of Minelab Go-Find 40. Photo & video | MD-Hunter Blog

So it's capable of using DD coils, just they wanted the model to have a fixed coil.

[Geotech]

The Go-Find uses what I call a "balanced inductor" method. Here is an excerpt from ITMD-3:

[Geotech]

Here is the prior section which sheds more light on what they are doing.

[Chase Goldman]

Thanks Carl, that puts that mystery to bed for me.

[Chase Goldman]

4 hours ago, phrunt said:

It is a mono coil.

Yep.  Just wondering how a Mono coil works in an induction balance design, but thanks to Carl, now I know as its not a traditional induction balance design.

Now that I do know, and based on the how the GoFind circuit is set up to accommodate the balanced inductor, it makes me scratch my head on why anyone even bothered with the GoFind DD hack.  It seems like so much trouble for a detector that was intentionally designed around the balanced inductor.  It seems that the effectivity of the Mars coil would have been degraded in this approach to the point that it would just make more sense to get a purpose built detector for similar cost if the goal was improved performance.  As far as I'm concerned, its another example of engineering for engineering's sake in the vein of "just because you can, doesn't necessarily mean you should".  But as an engineer, I still think its cool they did it.

As far as ML is concerned, it is also cool they pursued the GoFind as an actual product vs. just a proof of concept prototype.  Even in this simplest of detectors, plenty of innovation from the unique balanced inductor approach, the compact, foldable form factor, and the accompanying phone app, it looks like ML put a few "out there" concepts into the real world to see whether it might catch on.