Building a Metal Detector

[WM6]

But, will the DD coil have good discrimination for relatively big ferus objects?

This not depend on coil only but on applied detector too.

[RelicHunter88]

Thanks for explaining.

So, we can say that a DD coil is better for doing general stuff and other coil typer are for more specific jobs?

[Qiaozhi]

I read it.

So, to my understanding, a concentric coil will be more sensitive with better discrimination, but a DD coil will go deeper. Also the DD will work better in mineralized soil.

But, will the DD coil have good discrimination for relatively big ferus objects?
I do now want to dig straight done believing that i dig atop a chest full of gold, only to step into an old forgotten land mine.

Discrimination is about the same between the two types.

A concentric is better at pinpointing, but you need to overlap sweeps, as the sensitive area is around the RX coil.

A DD has a sensitive strip that runs from the front to the back of the coil. Hence it can cover the ground more quickly with less overlapping of sweeps, but pinpointing is worse. Often the target is located to one side, and it is advantageous to use a separate pinpointing tool. The DD is also better in mineralized soils because the RX and TX coils are the same size, and therefore the ground produces less imbalance in the detector than a concentric.

If you want to build your own coil, then a DD is easier to construct and balance. One disadvantage is that the coil calculator only supports circular coils, and you have to fudge the calculation for the DD.

[RelicHunter88]

Interesting.
Where can i find the formulas to calculate the cable gauge, turns, etc?

[Qiaozhi]

Interesting.
Where can i find the formulas to calculate the cable gauge, turns, etc?

The coil calculator is located at the top of the Coils Forum ->
http://www.geotech1.com/forums/showthread.php?t=17909

[RelicHunter88]

I have this calculator downloaded, but:

One disadvantage is that the coil calculator only supports circular coils, and you have to fudge the calculation for the DD.

I need the formulas and equations, or whatever, to calculate a DD coil.

[Davor]

Because of the mass production? Just wind it and check with a multimeter. Guess your multimeter has a L and C meter. Mine is over 20 years old and was not top of the line and it has it. Squeezing a round coil will not reduce its inductivity by much, so relax.

[Qiaozhi]

I have this calculator downloaded, but:



I need the formulas and equations, or whatever, to calculate a DD coil.

One reasonably accurate method is to take the average of the two diameters of one D-shape coil. But remember to enter this value as the radius into the calculator, not the diameter.

[RelicHunter88]

Will do that. Thanks!

[RelicHunter88]

One more question.

If a detector comes from the factory with a coil of certain diameter, let us say 10 inches, does this mea that the detector works better with coils of this diameter?

If we put a larger coil to a detector, will this make a detector work worse?
Of course a larger coil will be less sensitive, but can the detector work well with a larger coil?
For example, with a coil of 3 ft, a detector made for 10 inch coils, will detect targets at 18 - 15 ft depth, or worse?

[jap]

Important

This question normal, all the normal inexperienced asked him and do not ask other ,do not understand the answer and This is normal to --------- accommodate the story is not as large as the coil can go deeper--Especially in VLF And not in the case PI.
I hope reading may well protect against this frequent question the - ******I hope not to repeat this frequent question******
best time
J.

[Funfinder]

> is not as large as the coil can go deeper--Especially in VLF And not in the case PI.

Please decypher.


RelicHunter88:

Larger coil is better. DD coil is better.
Using 45cm Detech Excelerator with Garrett GTI 1500 gives
ca. 30% more depth compared to standard original coil
and covers more ground (= alot more finds per hour)


45cm coil tested under real conditions:

Smallest finds:
8mm lead ball at 10cm

medium finds:
7cm iron stuff at 50cm

Perhaps you better get professional military mine-detector.

btw. Is it allowed to collect ammuniton etc. stuff in Greece?
Of course the things you'll find are hopefully "defunctioned".

[RelicHunter88]

If the ammunition is manufactured before 1945, and does not contain explosives, gases, incendiary means or anything dangerous, you can collect it with a special permission. Otherwise you commit an act of terrorism.

I believe that musket balls and shells/bullets/cartridges from calibers not in production (made before 1945) can be collected without permit...

[jap]

Hi Funfinder
Diameters are saying about all that you mentioned I acceptable . ---but what it says,,

For example, with a coil of 3 ft, a detector made for 10 inch coils, will detect targets at 18 - 15 ft depth, or worse?

Previous reply was my answer

What is your answer?
best time
j.

[RelicHunter88]

My answer was if detectors are designrd to work with a coil of certain diameter, and if they will work good with other diameter coils.

I know that they are detectors that come with different coils of diferent diameters, but are these detectors made to work with these specific coils?