Very large DD coil

[dbanner]

Your design looks interesting, where did you get the idea from? It looks somewhat like the gpz 19 inch super D coil shape. Bigger coil bigger EMI effect. Required very good shielding.

[dbanner]

For easy nulling I suggest you pot the Rx coils independent of each other in their own respective housing which can be rigged with a slide mechanism to easily
adjust its null position with respect to tx coils.

[dbanner]

Cut grooves in ply along for each Rx will slide along perpendicular axis to tx coil. This make easy to fix null position

[dbanner]

They can then be tightened in place with plastic nut an bolts together with glue. If you want to try different Rx coil then all you have to do is disassemble from slide. This makes easier for experimenting with different coils for Rx.

[Krzychu_]

Coils are large and interact with each other on a long length and surface, and in addition must be electritically shielded. The fluxes of the variable electromagnetic field of both coils must be compensated and the entire system must have an appropriate phase of response for proper operation of identification and discrimination. Arrangement from the point of view of geometry seems simple, because symmetrical, but, to obtain this symmetry may prove to be the most difficult problem to solve ... It remains to experiment in the absence of external disruptions, that is in the field, outside the city.

[dbanner]

I would try super D geometric pattern first. Just scale up from 19 inches to 38 inches. Then cut out pattern and place on board with nails to wind coils. Both Rx coils will have same number of turns. Aim for your target inductances and use coil calculator to approximate no. Of turns. You can tune the coils to correct resonance so that at null, phases will be correct.

[Krzychu_]

I do not care about increasing the diameter of the coil and the range on large objects, only on the widening of the detection field. Coils for DFX are not resonant, although it may turn out that for one (higher frequency resonensity - 15kHz) they will work better ... (?)

[Krzychu_]

I still have a question about the configuration of the coils: what are the advantages and disadvantages of the following in relation to the DD system?
Thank you in advance for all the hints

[Gwil]

Go to the Geotech home page, then Metal Detectors, then Info. Click on 'Coil Basics'. Lots of information there.

[kt315]

i think first and second pics are same.

[dbanner]

They look the same for reversing the flow. The second one I think I've seen this coil before.

[Krzychu_]

Thanks for the tips, Gwil

[Krzychu_]

Does someone know how the windings of the receiving coils are wound and connected in the super-D system (in series or parallel)?

[Krzychu_]

Has anyone specified in any publication dependencies and restrictions on the wire diameter and number of turns in the coils of the receiving coil, while maintaining the parameters: sensitivity, level of interference, impedance matching to the input circuits, and the weight of the probe?

[Krzychu_]

wind round the winding by rope. take a wide one. take cheapest. paper or canvas done. may do several layers (of the rope). then
only wind around sticky scotch lenta, also several layers. after that put at the place and fill the epoxy resin.
you get the coils in air, not saturated by resin.

I chose a cotton braid, because cotton has the lowest dielectric permeability coefficient (~ 1.3 ... 1.4), however, the epoxy resin I use has very low viscosity and I am afraid that it will soak in cotton fiber.