Alternative ways to measure self resonating freqency of coil?

Status
Not open for further replies.
S

Signalglow

New Member
Hi guys!
I am going to wind a multi tapped toroid coil from 29.9mH to 156mH
I would like to know how i can measure the SRF without an oscilloscope?
I know that i could use a dip meter and figure it out fast, but i dont have that.

What i have is a DE 5000 LCR meter, with test tone frequencies 100 Hz / 120 Hz / 1 kHz / 10 kHz / 100 kHz
a function signal generator with sine, triangle, square wave, frequency 1HZ to 500KHz
and a standard multimeter, and an external soundcard for my computer with line in, line out.

Can i use these tools to get the SRF?

Help is much appreciated.

Best regards.
 
Why do you want to know anyway? - presumably this is for your graphic equaliser?, so of what interest is the self resonant frequency?.
 
Nigel Goodwin said:
Why do you want to know anyway? - presumably this is for your graphic equaliser?, so of what interest is the self resonant frequency?.
Click to expand...
Hi Nigel,
This is for a DIY Pultec equalizer.
I want to know this, so i can calculate the parasitic capacitance in the coil.

Best regards.
 
Picture of a grid dip meter. It is a oscillator and some coils. You can scan from a low frequency to a high frequency and see if your unknown coil resonates at some frequency. Very handy tool.
 
Signalglow said:
Hi Nigel,
This is for a DIY Pultec equalizer.
I want to know this, so i can calculate the parasitic capacitance in the coil.
Click to expand...

Again WHY? - how will that help you in any way?.

I suspect a grid dip meter wouldn't help much, as they are for RF, and you're looking at MUCH lower frequencies, which is why it doesn't matter.
 
Q - How do you couple a Dip Meter to a toroid coil?

A - In my experience, with difficulty.

JimB
 
Nigel Goodwin said:
Read above
Click to expand...
If I would/could read …..
I thought about putting the signal generator across the coil and also putting a a.c.-meter across the coil. But many meters will not measure 100khz ac.
what to do? ...….
Make a "RF probe" or a "demodulation probe" for your meter. Use the circuit from the internet. (ok most internet circuits do not work)
probe
Because we want to use it at a lower frequency than "RF" you might use 10x or 100x larger capacitors than normal.

Put the signal generator across the coil. The coil should short out the signal. Put the demodulation probe across the coil and set the meter to low voltage DC.
Sweep the signal generator and try to find a frequency where the coil 'opens up" and you get a large signal.
 
Nigel Goodwin said:
Again WHY? - how will that help you in any way?.

I suspect a grid dip meter wouldn't help much, as they are for RF, and you're looking at MUCH lower frequencies, which is why it doesn't matter.
Click to expand...
Okay i have not looked a lot into dip meters yet..
The reason is that i want to wind these coils with the less parasitic capacitance as possible,
Using a progressive winding technique (reverse winding technique)
So i would like to know the capacitance, so i can use this technique.
Best regards

ronsimpson said:
Do you have the part numbers or data sheet for the coils?
What equipment do you have? Scope? Signal generator?
Click to expand...
I want to wind the coil myself.
I have a signal generator, LCR meter (DE 5000), and a standard multimeter.
Best regards
 
Whatever measuring kit you connect to the coil will introduce further capacitance and skew the measurement. How will you account/compensate for that?
 
I have done this to reduce the capacitance.

The idea came from how high frequency flyback transformers are made. Slot winding makes the coil into several small coils.
 


Again, WHY? - wind the coils, build the graphic, job done - what difference do you imagine lowering the parasitic capacitance will make?. It's as if you've found the word on line somewhere, and imagine it's important for some reason.
 
alec_t said:
Whatever measuring kit you connect to the coil will introduce further capacitance and skew the measurement. How will you account/compensate for that?
Click to expand...
Well this is true, but i just want to get an idea.

Very interesting thanks for the tip, i found this technique.

Nigel Goodwin said:
Again, WHY? - wind the coils, build the graphic, job done - what difference do you imagine lowering the parasitic capacitance will make?. It's as if you've found the word on line somewhere, and imagine it's important for some reason.
Click to expand...
Trust me i want to just do the coil and just be done with it, but i really want to learn how to do this the best way possible, also for future projects.
What i want to avoid is unwanted oscillations, crosstalk and all the downsides of parasitic capacitance.
 

I'll repeat again - you're doing the coils for low frequency and high inductance - nothing you're worrying about is a concern, and the original coils certainly won't have been wound in any special way. I suspect you're also going to have a lot of 'fun' winding high inductance values on a toroidal former

You mentioned in the first post you're making a tapped inductor - that's going to make it MUCH worse than any imaginary capacitance issues, you need a separate inductor for each one.
 
Yes i cant wait to make this thing!
I guess this is the worst project i ever layed my hands on, the thing is, i am doing this by hand so this is a very time consuming task..
The inductor will be tapped, i dont have room for more inductors, but i will try it out, and see how it goes...
 
alec_t said:
...... so each section will be affected by its neighbours. I don't see how the self-resonant frequency of a section in isolation could be determined in that case?
Click to expand...
No you a totally right, the only way i can see this work is to check the parasitic capacitance after each layer , and use techniques on the next layer to reduce it.
 
Signalglow said:
Yes i cant wait to make this thing!
I guess this is the worst project i ever layed my hands on, the thing is, i am doing this by hand so this is a very time consuming task.
Click to expand...

Why build such an antique design?, anything remotely 'modern' uses gyrators instead of inductors, and these cure all the problems with inductors (none of which is parasitic capacitance though).

The inductor will be tapped, i dont have room for more inductors, but i will try it out, and see how it goes...
Click to expand...

So why all the concern about imaginary parasitic capacitance?, of vastly greater concern is that the inductors are all going to be coupled to each other as they are one big transformer. How tiny is your design?, there should be plenty of room for multiple inductors, which should be spaced apart anyway, in order to prevent interaction.
 
Status
Not open for further replies.

Similar threads

N
  • Question
Significance of resistance of the wireless power transmitter coil at resonance frequency
Replies
2
Views
730
danadak
  • Question
What can be a cheaper alternative to IC 5L0380R?
Replies
14
Views
5K
electronium
R
Help identifying alternative component Power Board
Replies
11
Views
2K
rjenkinsgb
K
  • Question
How to determine wiring of DC motor controller
Replies
13
Views
2K
Diver300
D
  • Question
How can a clamp meter be used to measure the amperage of a wire or cable from the phase and neutral of two strands?
Replies
6
Views
3K
Nigel Goodwin
Menu
Log in
Register
Cookies are required to use this site. You must accept them to continue using the site. Learn more…