Dual coil for mpp

[godigit1]

This is the way I did it.
Simply pre connect the inner coil before assymbly and put a damping resistor set up just like a normal coil damp the inner coil.
Make the connections to the outer coil final damp as you normally would.
I did this with two 3dss coils it worked pretty good but the wire I used was too fat for the 4 inch inner coil I had maid. so it kinda lost form and was ugly. So I scraped the inner coil.
It was a attempt at a self shielding dual field. No real ground testing done.
It worked that way for me but maybe I am missing something. Interesting to see the final results.

Denotes,
If you can get the srf in the inner coil before you connect to the outer is the only way you will get it .

Question for you guys in the know.
Would the dual field be considered a dual bandwidth coil if both coils have quite different SRF?
Say inner coil 1Mhx outer 500khz as a example.

[Denots]

having a bit of trouble with the math, It?s times like this I wish I had stayed in school


Is it as easy as inductance divided by capacitance?
how does the pi come into it and what does the big v with a tail mean?
if someone could point me in the right direction to decipher this I?d be ever so grateful

edit: so the v with a tail means radical notation I?ve just found out

[dbanner]

edited

[green]

having a bit of trouble with the math, It?s times like this I wish I had stayed in school
[ATTACH]47532[/ATTACH]

Is it as easy as inductance divided by capacitance?
how does the pi come into it and what does the big v with a tail mean?
if someone could point me in the right direction to decipher this I?d be ever so grateful

edit: so the v with a tail means radical notation I?ve just found out

Don't know how to get capacitance without measuring SRF. Use Rd=pi*L*SRF.

For a dual field I would short one coil and measure resonance and inductance of the other, then repeat for the other coil. Maybe correct maybe not?

[Denots]

Don't know how to get capacitance without measuring SRF. Use Rd=pi*L*SRF.

For a dual field I would short one coil and measure resonance and inductance of the other, then repeat for the other coil. Maybe correct maybe not?

I have an lcr meter so measuring inductance and capacitance of the coil is no problem, I’m just trying to get my head around the formula from the patent.

Been watching some vids on YouTube and I sort of understand what the radical notation symbol means, it’s a way to get the root, not sure how it’s used in the formula though but I’m chipping away

[waltr]

having a bit of trouble with the math, It?s times like this I wish I had stayed in school
[ATTACH]47532[/ATTACH]

Is it as easy as inductance divided by capacitance?
how does the pi come into it and what does the big v with a tail mean?
if someone could point me in the right direction to decipher this I?d be ever so grateful

edit: so the v with a tail means radical notation I?ve just found out

The 'radical' symbol means that the Square Root is taken of the value obtained inside (under)
Another way to write that equation is:
Square Root of L/ (PI * C). Your calculator should have the radical symbol. Play with it and if you take the square root of 2 the answer is 1.414.

PI (3.14) is required since this is a calculation of an AC (sine wave) signal.

[green]

Been wondering how to measure coil capacitance with a LCR meter. Found a site explaining how. To measure inductance, test frequency needs to be less than coil resonance. To measure capacitance, test frequency needs to be higher than coil resonance. It didn't say how much higher or lower to get a accurate reading. Does anyone know?

[dbanner]

That seems to be the case. I'm not sure why, but would sure like to know. I thought it was just a "ranging" issue with the meters, but apparently there is more to it.

[godigit1]

edited

Geuss I contradicted you sorry.
We are talking the same but reverse the order In did the inner one first thinking the outer would interfear.

Sorry for participating good luck Denots

[Denots]

The 'radical' symbol means that the Square Root is taken of the value obtained inside (under)
Another way to write that equation is:
Square Root of L/ (PI * C). Your calculator should have the radical symbol. Play with it and if you take the square root of 2 the answer is 1.414.

PI (3.14) is required since this is a calculation of an AC (sine wave) signal.

ok so with your help I think I’m getting somewhere, inductance is .120 capacitance is .430, if I’ve got this right I times capacitance by pi and then inductance is divided by the previous result which gives me 0.0888 and some change. I’m not 100 percent sure how accurate the readings are so will go back and measure again once I’ve got the formula.

Been wondering how to measure coil capacitance with a LCR meter. Found a site explaining how. To measure inductance, test frequency needs to be less than coil resonance. To measure capacitance, test frequency needs to be higher than coil resonance. It didn't say how much higher or lower to get a accurate reading. Does anyone know?

im not sure, I just clip the crocodile clips to either end of the coil and set the dial to the right position and the meter gives me a readout, I haven’t tried it with a frequency generator or anything like that.

That seems to be the case. I'm not sure why, but would sure like to know. I thought it was just a "ranging" issue with the meters, but apparently there is more to it.

I have two meters and one gives me a reading in the minus numbers so don’t think it’s that great but my other meter seems to be working just fine reading capacitance of a coil

Geuss I contradicted you sorry.
We are talking the same but reverse the order In did the inner one first thinking the outer would interfear.

Sorry for participating good luck Denots

thank you for participating, so am I right in thinking the signal hits the big coil first then passes through the smaller coil before returning to ground?

[godigit1]

thank you for participating, so am I right in thinking the signal hits the big coil first then passes through the smaller coil before returning to ground?

Sorry for my comment earlier bad bad night.
Anyway I think you are asking what the actual connection looks like?
Here is a crapy drawing but this is how I did the coils in series.
.
I think the damping procedure could probably be done both ways, I didnt do this but maybe could even use two adjustable damping resistor set ups and do both coils in secession either way.
Hope it helps

[dbanner]

Those coils don't appear to be in series, it looks like they are connected in parallel.
THe damping procedure is simple:
1 Measure the combined inductance and stray(self) capacitance of the two coils in series. From these figures, calculate main damping resistor.
2 Measure just the inner coil parameters of inductance and self capacitance. From these figures, calculate inner coil damping resistor.
3 You can make two damping tools to assist, just assemble the two coils in series, set the two damping resistors(use the damping tool setup) to the calculated values and connect to the coils as per schematic.
4 connect the coil and monitor output of preamp on oscilloscope while fine tuning the damping tool resistances to eliminate the ringing and thus tune the coil.

[godigit1]

Those coils don't appear to be in series, it looks like they are connected in parallel.
THe damping procedure is simple:
1 Measure the combined inductance and stray(self) capacitance of the two coils in series. From these figures, calculate main damping resistor.
2 Measure just the inner coil parameters of inductance and self capacitance. From these figures, calculate inner coil damping resistor.
3 You can make two damping tools to assist, just assemble the two coils in series, set the two damping resistors(use the damping tool setup) to the calculated values and connect to the coils as per schematic.
4 connect the coil and monitor output of preamp on oscilloscope while fine tuning the damping tool resistances to eliminate the ringing and thus tune the coil.

Your right Im still not thinking straight, food poisioning dehydrated.
Thanks for correcting me.
No one learns without being corrected. I appreciate people who are able to give constructive critiscism if more people cared enough to do so the world would be better for it.
corrected Photo

[dbanner]

That looks about right. There is one last step in the procedure above.
5 Once the search coils have been properly damped, remove and measure resistance of the damping tools and replace with fixed resistors of closest value.
Remember to adjust main damping resistor tool first, and then if necessary, the inner coil damping resistor tool last, in the above procedure.
It may seem counter intuitive, but I believe this is correct way.
Now some one may want to try this method and report back their findings. Seems simple enough, but you never know

[6666]

This coil is interesting to play with, the windings have to be in series and wound in same direction to add , mine is about 365 uH, but I have not damped it yet.