- 9th December 2011, 03:23 #1

- Join Date
- Dec 2011
- Posts
- 5
- Helped
- 0 / 0
- Points
- 315
- Level
- 3

## self resonant frequency of inductor coil

hi all.i have a coil made of ferrite pot core wound with 14AWG wire.i need to measure the self resonant frequency of that coil practically.thanks in advance.

- 9th December 2011, 03:23

- 9th December 2011, 06:05 #2

- Join Date
- Dec 2011
- Posts
- 6
- Helped
- 0 / 0
- Points
- 209
- Level
- 2

## Re: self resonant frequency of inductor coil

Hello, my knowledge is a little bit rusty but do you have a specific circuit you will place the coil in? as resonant frequency will be dependent on other components in the circuit and the easiest way to determine the resonant frequency is using a sine wave signal generator and an oscilloscope.

- 9th December 2011, 06:05

- 9th December 2011, 10:34 #3

- Join Date
- Dec 2011
- Posts
- 5
- Helped
- 0 / 0
- Points
- 315
- Level
- 3

## Re: self resonant frequency of inductor coil

hi ausie_burger_the_works.wire wound inductor coil has stray capacitance.with help of this it resonates.so i need to find that self resonant frequency.to excite my coil around that frequency

- 9th December 2011, 10:34

- 9th December 2011, 11:17 #4

- Join Date
- Oct 2011
- Location
- Bangalore
- Posts
- 922
- Helped
- 208 / 208
- Points
- 7,036
- Level
- 19
- Blog Entries
- 1

## Re: self resonant frequency of inductor coil

in myview the self inducatnce that you are talking will be in nano/pico heney and stray capacitances will be in Pico farads so if you compute the resonace frequency will be in the oder of 10^12 hz that is trea Hz or even above..... May be impossible to generate such high frequency from standard electronic devices.....I agree wil "ausie_burger_the_works"....that what I also knows

Good LuckHope the post will be helpful to you....

"Sharing is the best way of Learning"

- 9th December 2011, 11:23 #5

- Join Date
- Dec 2011
- Posts
- 5
- Helped
- 0 / 0
- Points
- 315
- Level
- 3

## Re: self resonant frequency of inductor coil

the coil is made of ferrite pot core wound with 40 turns,14AWG wire and i measured its inductance value 41.7uH using LCR meter,now i need to measure the coils own self resonant frequency due to its inter wire capacitance(stray capacitance). i need to check this practically.guide me to do so.

- 9th December 2011, 11:27 #6

- Join Date
- Oct 2011
- Location
- Bangalore
- Posts
- 922
- Helped
- 208 / 208
- Points
- 7,036
- Level
- 19
- Blog Entries
- 1

## Re: self resonant frequency of inductor coil

what is stray capacitance of such coil did u able to measure that ....as per I know it will be very low in the order of Pico or nano farad ...also you may be having some insulation resistance of arrround 20 Mohms now you need to put this parameters in the circuit ....and then try it out.... I can only say this much only

Good LuckHope the post will be helpful to you....

"Sharing is the best way of Learning"

- 9th December 2011, 11:37 #7

- Join Date
- Apr 2006
- Location
- Hyderabad, India.
- Posts
- 755
- Helped
- 119 / 119
- Points
- 7,719
- Level
- 20

## Re: self resonant frequency of inductor coil

Please see whether this paper from coilcraft is helpful.

http://www.inductors.ru/pdf/Doc363_MeasuringSRF.pdf

1 members found this post helpful.

- 9th December 2011, 12:44 #8

- Join Date
- Dec 2010
- Location
- Southampton and holiday cottage in Wensleydale (UK)
- Posts
- 3,457
- Helped
- 904 / 904
- Points
- 17,560
- Level
- 32

## Re: self resonant frequency of inductor coil

The coil you describe will have a self capacity of 100 PF or less (I would guess 5PF), so this puts its self resonance frequency above 250 KHz. Will your ferrite core still be working at this frequency?

Couple a RF signal generators output to the coil via a 5pf capacitor. Connect a high impedance RF measuring device across the coil and find the frequency that the voltage is a maximum. Repeat the measurement using a 10Pf coupling capacitor and find a slightly lower resonance frequency. Now you have Cs +5 pf for the first resonating capacitor and Cs +10 pf for the second. From these you can derive two equations to find the Cs.

Frank