At this point in time,i have to ask--what exactly are we looking for?

Found so far--> bifilar coil has lower self resonant frequency that that of the single wound coil.

Next is voltage difference between windings for both.


Brad

Each of my coils have 28 turns,and here is the voltages between turns of each coil

The single wound coil has 4VRMS across it,and starts with a voltage difference of 68mV RMS between the first and second turns (closest to center of coil)
As expected,the voltage increases between turns as we get closer to the outer most two turns.
At the outer two turns,the voltage difference between turns is 244mV RMS.

The bifilar coil has 4.24VRMS across it,and once again,as expected,has an average voltage between turns of 2.12VRMS--varying from 2.08 to 2.14VRMS between turns.

So far,nothing out of the ordinary between the two,except that the bifilar has a lower resonant frequency.


Brad

At this point I'm not sure that disconnecting the series link and measuring the capacitance between the two disconnected files is giving us the correct answer for the distributed capacitance.

At least I get different answers from measuring this way, and from solving the resonant frequency equation for capacitance using the measured resonant frequency and inductance.

Quote from: TinselKoala on April 16, 2017, 12:05:06 AM




Here's an inductance calculator that will show you that even the meter's connecting leads will probably have more inductance than that. 

http://www.consultrsr.net/resources/eis/induct5.htm

How are you measuring the inductance to be that low?

Your recent scopeshot of the ringing appears to show about 6.2 oscillations in 5 microseconds (2 divisions) which should be a frequency of about 1.24 MHz.

So taking the 1.22 nF capacitance and that frequency and working backwards for inductance, we should have about 13.5 microHenry. Even that seems low to me.  The bifilar coils and the monofilar coil I showed earlier each have inductance of around 700 microHenry. Are you sure we are seeing the coil ringing, and not your probe leads?

http://www.1728.org/resfreq.htm


Are those two traces at 40.5 MHz at the resonant frequency point?

Can you expand the trace of the single winding coil so we can read the frequency from the graticule? At first pass it looks to be a bit higher ( around 2 oscillations in one microsecond)than what you got with the ringing of the other coil ( around 6.2 oscillations in 5 microseconds).

The end of one winding,returns back to the center,and is connected to the beginning of the other winding.

QuoteYou are talking short PC board traces, for that low inductance.

I am using my DMM to measure the inductance value,and the leads are connected to the ends of the series coil pair.

QuoteWith 1.22 nF and 0.02 nanoH I get 1.0189 GHz. With 0.06 nH I get 588 MHz.

The capacitance value was taken with the two windings disconnected from one another-as Mags asked.
Once the two windings are joined together(series connected),then would not that capacitance value change?,as no capacitor has there two plates joined together,as the bifilar coil dose.


Added
Ok,went and checked capacitance again.
Bifilar coil has .66nF capacitance,and get this, -(yes,minuse) 50uF when the two windings are hooked in series. So guess we cannot measure capacitance when they are linked together.
So what dose that do or say about our capacitance value when the coils are hooked in series,and we are carrying out tests based around the two windings open circuit capacitance value?.

Inductance still reads .06mH
If i join the two DMM leads together,i get .00--nothing.


Brad

Quote from: TinselKoala on April 16, 2017, 01:33:45 AM
At this point I'm not sure that disconnecting the series link and measuring the capacitance between the two disconnected files is giving us the correct answer for the distributed capacitance.

At least I get different answers from measuring this way, and from solving the resonant frequency equation for capacitance using the measured resonant frequency and inductance.

Ah,see you were posting as i was typing.
Seems we both think this is the wrong way to go about it.

Brad