Litz wire size for coils

[green]

Thanks its good to be clear on these things, sometimes the wind in your picture is called flat basket wind, interesting that the PVC wire has the highest SRF.

Maybe because it has the lowest inductance.

[green]

Charted all of the coils I have made for the test. The target TC was 5.4usec instead of 5usec today, don't know why. Next test, chart signal amplitude vs target distance for the coils as is. Then shield some of them and with a longer lead line chart signal amplitude vs target distance. Targets, 1x1 inch aluminum can and something smaller. Maybe the smaller target will show a need for Litz wire. Maybe there is another test procedure that would show a need for litz wire. So far I'm not seeing it. Suggestions appreciated. Current profile, constant rate, 160usec on time, 1 amp peak.

[Chet]

Hi Green
I like your plan; smaller targets such as a .25 X .25 piece of aluminum may provide the answer.
Have a good day,
Chet

[6666]

Charted all of the coils I have made for the test. The target TC was 5.4usec instead of 5usec today, don't know why. Next test, chart signal amplitude vs target distance for the coils as is. Then shield some of them and with a longer lead line chart signal amplitude vs target distance. Targets, 1x1 inch aluminum can and something smaller. Maybe the smaller target will show a need for Litz wire. Maybe there is another test procedure that would show a need for litz wire. So far I'm not seeing it. Suggestions appreciated. Current profile, constant rate, 160usec on time, 1 amp peak.

You ask about the usefullnes of litz, I've seen Eric mention that one of the times litz has shown its advantages is with "invisible" gold nuggets

Here is a quote by somebody from 2004, talking about invisible nuggets and the problems of detecting them at that time.

There are still nuggets that hide in the ground mineral signal exclusion system of the Minelabs, and are now referred to as invisible nuggets. Some though, are even invisible without the surrounding ground matrix, and in this case, it appears that their invisibility is more the result of accretionary and precipitative processes involved in the nuggets formation, as opposed to holes in the detection system through which these gleamers continue to elude the Minelab PI user.

[green]

Charted all of the coils I have made for the test. The target TC was 5.4usec instead of 5usec today, don't know why. Next test, chart signal amplitude vs target distance for the coils as is. Then shield some of them and with a longer lead line chart signal amplitude vs target distance. Targets, 1x1 inch aluminum can and something smaller. Maybe the smaller target will show a need for Litz wire. Maybe there is another test procedure that would show a need for litz wire. So far I'm not seeing it. Suggestions appreciated. Current profile, constant rate, 160usec on time, 1 amp peak.

I charted three of the coils, coil volts vs target distance. Still not shielded. Shows the same as the decay curves, at delay times greater than 5usec the coils are very close. Smaller targets chart the same slope at lower amplitudes. I would expect the minimum delay time to be at least 5usec after shielding so I'm not seeing an advantage to using Litz wire over AWG28 solid. Maybe AWG24 solid would be alright with delays above 10usec. For larger size wire stranded or Litz could be necessary. Once I shield the coils I can't go back and test not shielded, so I'm hoping someone can tell me what I'm missing or should do different before I shield some. A couple things that could be different that I think shouldn't matter, amplifier closed loop band width and I'm testing coil stationary not moving. I've read recommending AWG32 or 34 for a minimum so I think I'm probably missing something. I'm not suggesting using solid over stranded, I did the test because I have a lot of AWG28 magnet wire and wondered if the wire acts as a target. It appears that it does at short delay times.

[Chet]

Hi Green
I like your test results. What causes the separation between coil D and coil E start times in your chart? What kind of shielding do you plan to use?
Have a great day,
Chet

[green]

Hi Green
I like your test results. What causes the separation between coil D and coil E start times in your chart? What kind of shielding do you plan to use?
Have a great day,
Chet

I'm guessing it's the wire acting as a target. Litz comes out of saturation first, then AWG 28, then AWG24. EZ-SLIDE graphite coating.

[Chet]

Hi Green
Sounds reasonable and looks like a good plan.
Thank you,
Chet

[6666]

I'm guessing it's the wire acting as a target. Litz comes out of saturation first, then AWG 28, then AWG24. EZ-SLIDE graphite coating.

With the EZ Glide what ohms per inch do you get ?

[green]

With the EZ Glide what ohms per inch do you get ?

200 to 600 ohms is typical, I'll post what I get this time with the other information. My can says EZ-SLIDE. I use the brush on. Haven't tried the spray.

[6666]

200 to 600 ohms is typical, I'll post what I get this time with the other information. My can says EZ-SLIDE. I use the brush on. Haven't tried the spray.

Thanks, I had a look at the factory website, there appears to be several different products, one they call "paint" and something else
and they have different ratio's 20:80 ~ ~ 80:20 I assume thats the amount of graphite in the mix
do you know which one you have ? wish we had this in Australia.

[green]

Thanks, I had a look at the factory website, there appears to be several different products, one they call "paint" and something else
and they have different ratio's 20:80 ~ ~ 80:20 I assume thats the amount of graphite in the mix
do you know which one you have ? wish we had this in Australia.

Looked up what I have, EZ-SLIDE 9512, Said it's for spray application but I've been brushing it on. It's what the local Tractor Supply had. Works good for painting the under side of lawn mower decks, helps keep the grass from sticking. Couldn't find the mixture ratio.

[6666]

Thanks you have the Graphite Alkyd Coating.
and is the waterborne formula the other is a oil based paint


Found some more info, the different graphite blend ratio is for the dry powder only not the paints.

[green]

Charted some data with shielded coils. Made two rings to sandwich the coil between. Ring, 175IDx275mmOD. Easily covers coil. Got about 800 ohms/inch for the shield. Moving hand near coil not shielded caused a signal change about the same as the nugget at 2 inches. No change shielded. Had to change the lead wire from 12 inches twisted pair Teflon coated to 36 inches twisted pair pvc coated to get the resonance down to 1MHz for the test. Same results as the tests I've done in the past, shielding didn't effect signal strength. Don't think could sample any sooner with Litz wire compared to the other wires with the resonance down around 1MHz. Reply#95 covers what might be the benefit of using Litz. The picture says glue painted side to poster board, the poster board is painted so glue painted side to craft foam.

[6666]

Got about 800 ohms/inch for the shield.

Thanks.