Iron core choke measurement

[Steve Blackdog]

Hi folks,

I have a small choke, that was previously fed by a 92v secondary putting out around 2A. How to I measure the Henrys?

I see iron core chokes on schematics with no value stated, so I am confused

[Helmholtz]

See here:

https://www.dalmura.com.au/static/Ch...easurement.pdf

Courtesy of MEF member trobbins.

[vintagekiki]

The PU frequency response can be recorded similarly.

[trobbins]

An up-to-date method of measuring PU frequency response for impedance of winding is to use a soundcard and REW software - I've used that a lot this year - very accurate and automated and over a frequency range as wide as your soundcard. There is an example plot in the article linked by Helholtz.

[vintagekiki]

You forgot that not all users have a sound card and REW software.

[Enzo]

Um... didn't the OP specify an iron core choke rather than a pickup?

[vintagekiki]

Specify is PU.

[Helmholtz]

PU serial impedance response is not the same as PU transfer response.
One of the problems is that an external signal generator cannot be placed between the PU inductance and the self-capacitance like the real EMF.
In other words, impedance measurement sees the PU as a (damped) parallel resonant circuit, while a real PU acts as a serial resonant filter as seen from the EMF.

I agree with Enzo, that this isn't the right place to discuss PU measurements.

[trobbins]

PU is the DUT (device under test) in the schematic in post #3. I thought vintagekiki was referring to a pickup, but maybe not, but either way the schematic with 'PU' is for an impedance response without DC - and I guess vintagekiki is forgetting that not everyone has a signal generator or an AC voltmeter with a wide bandwidth.

[trobbins]

For a pickup winding, the impedance frequency response as generated by REW can identify the inductance component by inspecting the low frequency impedance portion of the plot, and can identify the self-capacitance component by inspecting the higher frequency impedance portion of the plot (above the main resonant peak of impedance). So it is a means to extract the main bulk equivalent circuit model component values, at the excitation voltage applied by the soundcard (which may influence the REW calculated inductance value).

PS, in the choke impedance plot in the post #3 link, the choke winding bulk capacitance is calculated by REW as about 125pF in the frequency range from 30kHz to 50kHz where the phase indicates the choke is acting principally as a capacitance.

[Helmholtz]

..the impedance frequency response as generated by REW can identify the inductance component by inspecting the low frequency impedance portion of the plot, and can identify the self-capacitance component by inspecting the higher frequency impedance portion of the plot (above the main resonant peak of impedance).

Thanks, understand.
That's how the big HP impedance analyser worked I used in my former company.

[vintagekiki]

#10

When guitar PU and amps is developed (many years ago) did not exist sound cards and REW software.
I'm afraid you got lost somewhere in calculations and measurements.
Please explain me which PU and guitar speaker reproduces the frequency range from 30kHz to 50kHz?
It's something new, I didn't know.
What the human ear hears (registers)? ^{nothing personal)}

[Sticktosharingschems]

#10

When guitar PU and amps is developed (many years ago) did not exist sound cards and REW software.
I'm afraid you got lost somewhere in calculations and measurements.
Please explain me which PU and guitar speaker reproduces the frequency range from 30kHz to 50kHz?
It's something new, I didn't know.
What the human ear hears (registers)? ^{nothing personal)}

Are you contending that the classic designers weren't aware of parasitics, ultrasonics or stability and their potential implications in the Audible range? "Member insult deleted"
Such a stupid, useless comment.

[trobbins]

Please explain me which PU and guitar speaker reproduces the frequency range from 30kHz to 50kHz?

The example choke in the link had a main resonance at 10kHz, so the shunt capacitance only shows itself at a higher frequency - in that case it was about 30-50kHz. If a PU had a main resonance at 1kHz, then its shunt capacitance can be likely measured at 3-5kHz. I don't have any pups to measure just at the moment, so can't post an example, but that should be in another thread anyway. For common valve amp power supply chokes the self resonance is typically down around 2-3kHz from the few I have measured.

[vintagekiki]

13

Boy I'm afraid you wrong portal.
I'm nothing contending unlike you, I know.
What you knew, that you wrote and very well present yourself.
If I may ask you, what is your references when you are so confident, unless you are a troll.