Nuggetfinder Z Coils For GPZ 7000

[geof_junk]

New for 2020

 

Nuggetfinder Z-Search Coils

 

Release delayed until September 2020

 

 Our new 12" Round Z-Search DOD Coil is coming, however the Covid-19 situation has resulted in some delays with production.

  The 12" Round will be the first of several coil sizes we will be producing for the Minelab GPZ7000.  

 

The 12" Round Coil pictured below weighs in at approximately 1000 grams (Weight Excludes Lower Shaft) 

The 12" Round Z-Search DOD has been designed to at least match the standard 14"x13" for depth and sensitivity across a broad range of target sizes.

The 12" Round will suit any prospector looking to reduce the weight of the GPZ7000 without compromising performance and coil stability.  

 

Water Resistant to 1m

Supplied with Lower Shaft 

 

The standard 14 inch MineLab GPZ7000 weight in at 1500 gm this works out to a 33% reduction in weight and is of the DOD design that the GPZ7000. That Minelab made because it was the most suited for it. 

[AussieMatt]

5 hours ago, phrunt said:

I can't see it being a good seller and a big disappointment to those that were waiting on it.

People will buy it for the same reasons they have previously purchased NF coils (& other aftermarket coils) that are similar sizes to Minelab stock coils - perceived or real superior performance, lighter weight, brand reputation/loyalty, Aussie made (if from Aust) etc.  etc.

Those that have taken the X Coil jump will no doubt be unimpressed! They already have a good selection to choose from. But I reckon for every one GPZ user that's taken the mod path to enable use of X Coils there's probably at least 5 that haven't or won't, maybe a lot more than that.

Lighter coils that are plug & play will sell (if the performance is there & price is acceptable) regardless of size/s & NF will bring out different sizes once this first one is out there, just like they've done with the Evo coils.

 

[WesD]

Jasons comment above makes a lot of sense. The stock size is probably all minelab allowed them, for whatever reasons, if they wanted to use their chipped cord.

What a disappointment ?

[Chet]

Here are some thoughts and trade-offs that companies may consider on how to reduce the weight of a coil. 

Use smaller gauge or less copper wire. Bunch wound coils use a little less wire than Spiral wound coils which can reduce performance. Smaller gauge wire in the transmit winding could reduce overall performance.

Use less plastic by reducing the overall thickness and strength of the housing and the shaft attachment area. 

Use lighter weight foam or other material to fill and support the windings within the housing. Some lighter weight fillers break down with age and heat.

Consider method to prevent false signals when bumping into rocks and brush.  The internal coil and foam mass in the Minelab 13” x 14” coil is suspended in the center under the shaft mount by cushions. It does not touch the surrounding housing. Other standard methods use glue/epoxy to rigidly tie the coils down to prevent any movement. The amount of heavy material vs. foam used can add considerable weight.  

Provide the coil without an optional skid plate will reduce the weight of a 13” coil by about 120 grams or 4.3 ounces.

The final trade-offs must result in a coil that will satisfy the customer. 
 

[flakmagnet]

As usual Jason and Chet and Reg make good points.
If the new coil has any kind of improvement in performance and is lighter, I'm in.

[jasong]

Hey Chet, since ZVT is kinda VLF-like (AC, not pulsed), I wonder if there couldn't be weight savings by using Litz or even just stranded wire since the skin effect will mean a lot of the current is conducted near the surface of the wire and so the resistivity of a stranded wire will be lower than that of a solid wire of equivalent gauge since there is more surface area.

Thus, you could use the same number of turns in the coil so coil inductance would not change but the stranded wire could be smaller diameter. Smaller wire but with the same resistance means current would stay the same in the RL circuit, so the control box wouldn't see any difference. Everything should be equivalent to the stock windings, but weight would reduce.

Or do they already use stranded wire? Or is the GPZ frequency low enough that stranded wire is higher resistance?

[Chet]

In the ZVT function there is an abrupt square wave transition between reversing high positive and high negative current levels. The transition periods are a high frequency function that requires Litz wire for efficiency.  

The Minelab and Russian GPZ coils both use Litz wire in the Transmit and Receive windings to reduce high frequency energy loss. 

Magnetic eddy currents from nearby wires have opposite polarity and cause energy loss in coil windings.

There is less energy loss in single layer Spiral Litz windings since there are no adjacent wires above and below the single layer. 

Some energy loss still occurs in single layer Spiral windings. That loss could be reduced considerably by a spacing of five wire diameters between each winding but there is not enough room in the coil housing to allow this much separation.
 

[jasong]

Ok, that makes sense, thanks.

I had another question - reducing windings to save weight decreases the inductance of a coil, how about removing some windings and then increasing the coil inductance back to specifications by increasing the permeability of the core to make up for the loss of windings? Iron shaving impregnated epoxy for instance, or thin inclusions of Metglas (or Mu metal, whatever could be available) since these coil are pricey already anyways. I think that would be lighter than the windings it replaces. 

Slightly smaller diameter wire could also be used since the resistance with less wire length would decrease and to keep current at prior specs the wire diameter could be decreased slightly to add a small bit of resistance.

As we see with your cable mod, a material that might otherwise be detected will not interfere if held immobile in relation to the windings.

I'll stop asking after this so as to avoid offtracking the thread. 

[Steve Herschbach]

No worries Jason, great info, and not a lot more to say about the NF coil until somebody gets their hands on one.

Minelab GPZ 14 guts: