WHITES DUAL FIELD COIL

[daverave]

i have now completed 2 surf pi detectors....one with normal mono coil and the other with dual field coil....and i must say the mono coil go's deeper than the dual field coil on gold items so im still not convinced by dual field...and i feel that i will stick to mono coils in the future.

[Waikiki_Sweep]

Also I have to tell that Dual field coil is relatively light weight.
Looks like it filled with foam so you can see it floating in water.
You have to apply some force to push it down to the ocean bottom.
(Heavier neutral buoyancy coils accessible too)

[Waikiki_Sweep]

There is no reason to put resin into PI coils. Only balanced coils like VLF are required hard and strong construction to keep that precise balance.
PI coil you can bend, shake, deform and it will be working anyway. So you can use small amount of light weight materials to build the coil and make it as light as you can.
Light coil is a gift!!! You will see it in the field after sweeping a two pounds "brick" of epoxy for several hours every day and finally ends up with arthritis.

[Carl-NC]

Actually, the TDI runs 300uH and the SMPI is 240-250uH as I recall. The TDI has a very limited ability to reject iron, mostly in mild ground.

[daverave]

i guess the tdi will have lower inductance as it detects small nuggets...is it true tdi can reject iron ????

[Carl-NC]

Same configuration, just slightly different inductances.

[daverave]

are the whites tdi and surfmaster dual field coils the same...or is tdi coil different configuration ????

[daverave]

what a very bad time ive had putting resin in my coil !!! i rushed the job and didnt make sure the coil was perfectly level so resin was uneven and poured out onto the carpet and over my work bench and also the small inner coil must have come unstuck and lifted so i could not get perfect covering of the coil with resin...it was a total nightmare cause of my inpatience....my room carpet ruined in our rented flat.

[Jose]

ive now sorted out my dual coil and very happy with the results im getting from this coil

Daverave.
Glad the proper functioning of your coil.
The values I posted were the ones who were in my MD, but all my coils and detectors are made in house, so may be far from reality.
However, the general rule for the damping resistor, is the largest value that does not produce oscillations.
Again, I'm glad that you get good results, I invite you to publish the final scheme, so we can all appreciate.
A Cordial Greetings
Jose

[daverave]

I performed the dual field coil as follows:
The two coils have the same number of turns.
A coil of 30 cm, 16 turns, and the other 20 cm diameter, 16 turns.
Both coils are in series.
The center coil leads damping resistance.
At the ends of the coil carries another damping resistance.
The resistance values are experimental buffer.
The advantage is a better detection of small objects.
See the diagram below.
Jose[ATTACH]26732[/ATTACH]

i tried the 3.9k damping resistor for the small coil as in your diagram but it did not work but produced bad ringing so i tried resistor of less than 500 ohms and no ringing.

[daverave]

ive now sorted out my dual coil and very happy with the results im getting from this coil

[daverave]

im just finishing my dual field coil and almost ready to pot in resin but im finding it difficult to get perfect waveform on the small coil...i used about 3.8k for the damping resistor but when i adjust the damping for the large coil without ringing then the small coil damping is out with ringing....i cant seem to get perfect non ringing balance between the two coils.

[daverave]

it the original one same like from pulsdetektor.de or new pulsdetektor.biz
[ATTACH=CONFIG]27281[/ATTACH]

hi bernte_one
can you tell me whats the advantage of this coil compared to normal round coil ?????

[bernte_one]

it the original one same like from pulsdetektor.de or new pulsdetektor.biz

[daverave]

hello daverave

if you make a dualfield coil use the photo from kt315
connect both coils in serie (in same winding direction)

to improve the simple dual field coil form the inner coil
to a tri-spiked star
you get a coil with sections of higher and lower magnetic field concentration
it ist a good mix for ground penetration and small objetct sensivity

http://www.detector-trade.de/uploads/tx_dmfgalleria/produktbild-dtipuls-antares-01.jpg

regards

how is a tri spiked coil wound...do you have any photos of windings ????