Subject : Re: measuring the resonant frequency of the secondary
Date : Sat, 10 Jul
2004
21:50:40
-0600
Subject :
Re: measuring the resonant frequency of the secondary
Original
poster: robert heidlebaugh
<rheidlebaugh@desertgate.com>
You need a 500 ohm resistor a signal generator and an AC voltmeter. The resistor
is used to prevent copper wire shorting out the signal generator by placing it
in series with the coil to be tested. You measure the voltage across the coil or
resistor . At resonant frequency the voltage across the coil will raise and the
voltage across the resistor will drop. start measurements at a frequency below
your lowest expected frequency. If you
start above you will find harmonics not the fundamental frequency. Low voltage
signal generators tend to be difficult to use. A generator that puts out at
least 15 volts or more is best. Measure the secondary and adjust the primary to
match. This will give you your starting point to tune the system for best
results. These tests are done with the POWER OFF on your TC system. if you apply
power your TC it will destroy your test equipment and you. Robert H.
> From:
"Tesla list"
<tesla@pupman.com>
> Date: Thu, 08 Jul 2004 16:34:18 -0600
> To: tesla@pupman.com
> Subject: measuring the resonant frequency of the secondary
> Resent-From: tesla@pupman.com
> Resent-Date: Thu, 8 Jul 2004 16:40:05 -0600
>
> Original poster: "Anthony"
<ant17@optushome.com.au>
>
> hi guys i hoping you could help me i have my sstc secondary and primary hooked up to
>signal generator and i am trying to measure the resonant frequency of it by having the
>primary hooked up to the sig gen and my oscilloscope probe on the toroid and then
>checking for peaks in the waveform because i think you should see ringing peaks in the
>waveform question is am i on the right track or not if you could help i would be grateful.
Date : Tue, 20 Jul
2004
08:14:03
-0600
Subject :
RE: measuring the resonant frequency of the secondary
Original
poster: "Steve Conner"
<steve.conner@optosci.com>
>You have to use a signal generator with very low output impedance to see the
peaks >clearly.
To check the tuning of a complete TC (primary and secondary together) I like to
use a ferrite transformer to couple the output of the sig gen to the primary. I
connect the sig gen to a 30 turn winding on a ferrite ring, and drive the TC
tank circuit from a single turn secondary (an alligator clip lead passed once
through the ferrite ring, and hooked across the TC spark gap)
This works great with an old HP 200 style tube oscillator- these have a generous
output of ~40V into 600 ohms. It actually excites the TC enough that I can pick
up the secondary output from a scope probe held in mid-air about 2ft away, and
see the resonant frequencies that way. I can also see the oscillator's output
voltage being loaded down at the resonances.
To test the secondary alone, you can base drive it directly from the oscillator
(connect one lug of the oscillator output to the secondary base, and the other
to a ground plane, or the AC line ground.) . Steve C.
Date : Tue, 20 Jul
2004
21:09:01
-0600
Subject :
Re: measuring the resonant frequency of the secondary
Original
poster: "Antonio Carlos M. de Queiroz"
<acmdq@uol.com.br>
Tesla list wrote:
>
> Original poster: "Steve Conner"
<steve.conner@optosci.com>
>
> >You have to use a signal generator with very low output impedance to see the peaks
>clearly.
>
> To check the tuning of a complete TC (primary and secondary together) I like
> to use a ferrite transformer to couple the output of the sig gen to the
> primary. I connect the sig gen to a 30 turn winding on a ferrite ring, and
> drive the TC tank circuit from a single turn secondary (an alligator clip
> lead passed once through the ferrite ring, and hooked across the TC spark
> gap)
>
> This works great with an old HP 200 style tube oscillator- these have a
> generous output of ~40V into 600 ohms. It actually excites the TC enough
> that I can pick up the secondary output from a scope probe held in mid-air
> about 2ft away, and see the resonant frequencies that way. I can also see
> the oscillator's output voltage being loaded down at the resonances.
>
> To test the secondary alone, you can base drive it directly from the
> oscillator (connect one lug of the oscillator output to the secondary base,
> and the other to a groundplane, or the AC line ground.)
This would probably work well also with my suggested square wave excitation.
Something to try. Instead of a buffer after the oscillator, I have tried too to
just shunt the output of a 50 Ohms, 10 V generator with an 1 Ohm resistor. But
this reduces the driving voltage to 196 mV. A transformer with 7:1 turns ratio
would also reduce 50 Ohms to 1 Ohm, but with an output of 1.43 V. Antonio
Carlos M. de Queiroz.
Date : Tue, 20 Jul 2004 21:09:36 -0600. Subject : RE: measuring the resonant frequency of the secondary
Original poster: "Malcolm Watts"
<m.j.watts@massey.ac.nz>
On 20 Jul 2004, at 8:14, Tesla list wrote:
> Original poster: "Steve Conner"
<steve.conner@optosci.com>
>
> >You have to use a signal generator with very low output impedance to
> >see the peaks cleary.
>
> To check the tuning of a complete TC (primary and secondary together)
> I like to use a ferrite transformer to couple the output of the sig
> gen to the primary. I connect the sig gen to a 30 turn winding on a
> ferrite ring, and drive the TC tank circuit from a single turn
> secondary (an alligator clip lead passed once through the ferrite
> ring, and hooked across the TC spark gap)
>
> This works great with an old HP 200 style tube oscillator- these have
> a generous output of ~40V into 600 ohms. It actually excites the TC
> enough that I can pick up the secondary output from a scope probe held
> in mid-air about 2ft away, and see the resonant frequencies that way.
> I can also see the oscillator's output voltage being loaded down at
> the resonances.
>
> To test the secondary alone, you can base drive it directly from the
> oscillator (connect one lug of the oscillator output to the secondary
> base, and the other to a groundplane, or the AC line ground.)
It is important when doing this for measurements of a scientific nature that the
generator presents as low a source impedance as possible. A 600 Ohm source will
seriously degrade the Q of a resonator with an ESR of a couple of hundred Ohms.
I think you should still be using your drive transformer if this is what you are
intending to do. The generator I use has a defined 0.5 Ohm output impedance
together with overcurrent (limiting) indicator so I know when the source
impedance is deviating from its ideal. Malcolm.
Date : Wed, 21 Jul 2004 07:20:38 -0600. Subject : RE: measuring the resonant frequency of the secondary
Original
poster: "Steve Conner"
<steve.conner@optosci.com>
>It is important when doing this for measurements of a scientific nature that
the >generator presents as low a source impedance as possible.
Well, I suppose it will mess up the "Q" completely, but it still seems to be OK
if you only want to measure the resonant frequency. Steve C.
Date : Wed, 21 Jul
2004
11:53:07
-0600
Subject :
Re: measuring the resonant frequency of the secondary
Original
poster: Ed Phillips
<evp@pacbell.net>
"Something to try. Instead of a buffer after the oscillator, I have tried too to
just shunt the output of a 50 Ohms, 10 V generator with an 1 Ohm resistor. But
this reduces the driving voltage to 196 mV. A transformer with 7:1 turns ratio
would also reduce 50 Ohms to 1 Ohm, but with an output of 1.43 V.
Antonio Carlos M. de Queiroz"
I use an output transistor from a very cheap transistor radio for the
purpose. Seems to be useful up beyond 400 kHz, much to my surprise. Ed.