Coil question?

[green]

hi green.
why in the pi detector. When I increase the size of the coil. the detection distance does not increase much or nearly the same as that of a coil at least the size. In particular coil of size 1m.
A lack of electrical voltage in the coil or a problem in the receiver

Hi sbalio,

What coil sizes are you comparing? Is the coil inductance the same? What is the target distance you are comparing at? Do you have an answer to any of the questions?

[sbalio1]

hi green
I used several coils with many types of threads: the best coil obtained by a good sensitivity to medium formats in particular.
I did it as a litz 5 * 5 * 016
coil 70 cm compared to the size of 20 cm and was the best result between all types of reels of this size. From 1.60 to 1.75 meters
But in a reel of 1 meter with all kinds of reels did not exceed this distance to the size of 20 cm.In addition, some reels the size of 1 meter corresponded to the size of 20 cm less than 1.5 meters. Same thing for the size of 25cm

yes the inductance of the coil is the same

[bbsailor]

bbsailor Thank you

I will follow the subject to understand how the distance is measured in relation to the radius of the coil.Because I didn't understand it correctly

See this tutorial on coil sizes and types.
http://www.mdhtalk.org/tutorials/coi...archcoils-.pdf

Different coil types and sizes, like mono, DD, DOD or figure 8 work best on different soil types and hunting conditions. On wet beach sand you want to use a delay of 15 uS or more to not detect the wet sand as a target. On dry sand you can try to use the lowest amount of delay to find smaller targets.

Different coil types such as mono coils require more overlap of search patterns to not miss deep targets at the tip of the coil penetration pattern typically deeper in the center of the coil. DD coils have a different penetrating pattern.

The tutorial should help.

Joseph J. Rogowski

[sbalio1]

Thank you.bbsailor .green

To understand my intention
no problem of detection with coil like 20 cm and 40 cm and also with 75 cm. but the problem is with coil 1m or more .a the size of 20 cm metal


did not spend a lot of time trying to classify a bigger size of 70 cm but a few attempts
It's the quality of the threads that I made.
To reduce the coil capacity.
And to get a fast response coil and little noise and more stable
The focus was on big coils.

[sbalio1]

https://www.youtube.com/watch?v=BNyEBfy8AXI

https://www.youtube.com/watch?v=bULrStpPgRE&t=32s

[green]

hi green
I used several coils with many types of threads: the best coil obtained by a good sensitivity to medium formats in particular.
I did it as a litz 5 * 5 * 016
coil 70 cm compared to the size of 20 cm and was the best result between all types of reels of this size. From 1.60 to 1.75 meters
But in a reel of 1 meter with all kinds of reels did not exceed this distance to the size of 20 cm.In addition, some reels the size of 1 meter corresponded to the size of 20 cm less than 1.5 meters. Same thing for the size of 25cm

yes the inductance of the coil is the same

Can you give an example? Coil A diameter_____? distance target X detected with Coil A______? Coil B diameter______? distance target X detected with Coil B______? What is target X______?

See you have added a couple replies that I hadn't read yet. Maybe they will answer some of my questions.

[sbalio1]

hi green.
coil A;75cm. target 20cm .detected 1.75m
coil B;100 cm.target 20cm.detected 1.5m

[green]

hi green.
coil A;75cm. target 20cm .detected 1.75m
coil B;100 cm.target 20cm.detected 1.5m

Thanks, just what I was looking for. For interest I'll chart the two coils with HyperPhysics. If you still have the two coils, could you measure inductance and resistance?

[sbalio1]

I have an ESR tester that gives the inductance .frequency resonance of the coil and the resistance .il m gave
coil A 2.7 ohm.375 uh
coil B 3.4 ohm.360 uh

[Koala]

Hi

See this tutorial on coil sizes and types.
http://www.mdhtalk.org/tutorials/coi...archcoils-.pdf

Different coil types and sizes, like mono, DD, DOD or figure 8 work best on different soil types and hunting conditions. On wet beach sand you want to use a delay of 15 uS or more to not detect the wet sand as a target. On dry sand you can try to use the lowest amount of delay to find smaller targets.

Different coil types such as mono coils require more overlap of search patterns to not miss deep targets at the tip of the coil penetration pattern typically deeper in the center of the coil. DD coils have a different penetrating pattern.

The tutorial should help.

Joseph J. Rogowski

Reading through the PDF

A lot is copy and paste from the Internet.

Unfortunately the Internet is full of information Thats not checked

The wide scan vs concentric diagrams are wrong. Looks very like minelabs advertising images. I have checked my concentric 100% bogus

Four windings in a DD

A quarter goes from 5" to 14" with a 5" to 15 coil. Strange I get close to 10" In the ground with my home made Bandido on a similar size coin and a 5.5" coil

[green]

I have an ESR tester that gives the inductance .frequency resonance of the coil and the resistance .il m gave
coil A 2.7 ohm.375 uh
coil B 3.4 ohm.360 uh

HyperPhysics predicts the 100cm coil would have the same signal strength at 200cm(you are getting 150cm detection distance) as the 75cm coil does at 175cm. 100cm coil has more resistance(probably less peak current), less inductance so its going to have a little less signal. Not enough to see the difference you are seeing. Maybe noise or something else is causing that much lose in distance?

[Carl-NC]

See this tutorial on coil sizes and types.
http://www.mdhtalk.org/tutorials/coi...archcoils-.pdf

I agree with Koala, that's a poor tutorial with a lot of bad information.

[sbalio1]

hi green
I already tried coil 100mm.resistance 1.3 ohm. with a copper wire 1mm pvc
The result was better than 1.5 meters but did not exceed 1.7m
Is the final size range of 20 is 1.7 meters or an increase in induction may increase more
in your opinion .
How to exceed 2 meters with 20 cm of volume with coil of 100 cm
How much can be .induction of the coil.and resistance.
where what size of coil.Is it possible as an example

[green]

hi green
I already tried coil 100mm.resistance 1.3 ohm. with a copper wire 1mm pvc
The result was better than 1.5 meters but did not exceed 1.7m
Is the final size range of 20 is 1.7 meters or an increase in induction may increase more
in your opinion .
How to exceed 2 meters with 20 cm of volume with coil of 100 cm
How much can be .induction of the coil.and resistance.
where what size of coil.Is it possible as an example

Hi sbalio
I'm replying, not because I know the answer but like you I wonder why the larger coil detects at less distance. The 100mm coil predicts twice the signal of the 75mm coil at 2meters. Should give an increase in detection distance of 20cm+ if inductance and noise stayed the same. If noise doubles with the 100cm coil, detection distance shouldn't change. Monitoring integrator out with a scope should give an indication of change in noise level.

I've charted target distance vs receive amplitude(same as HyperPhysics chart) by monitoring integrator out with a digital voltmeter. What PI circuit are you using? Do you have a scope? 30cm coil is the largest I've made so I'm trying to learn something with this thread. Maybe someone else could suggest what might be causing lose of detection distance or what to try to find out.

[green]

Hi sbalio
Was looking at some comparison data, measured vs HyperPhysics I did awhile back. Tracks close out to coil diameter on all coils. Wondering if target size vs coil size might cause measured data to be less than predicted at the longer detection distances. Zapped my bench circuit awhile back, wondering if you could compare your 75cm and 100cm coil with a larger target, maybe 40cm target. Could be target size vs coil size does make a difference or I didn't take enough care when measuring the data. If you get a longer detection distance with the 100mm coil with the larger target I'll put something together to remeasure the coils with a 25mm and 50mm target to see if the larger target tracks better at the longer distances.