LCR metter for EQ project

[kryz]

Hi,

This is my first post so a salute to all!

I am studying electronics so if i say something strange/rare pardon i am self learning with books.

I am in the part of inductance and electromagnetic and for my project i think i do need a LCR meter.

I got some hand made coils, sames values as the neve 1073 eq, which i love btw.

They are multi tapped coils at 2H, 1H, 400mH, etc, many points to adjust the frequency of the eq.

The LCR meters with full range are quite expensive but if is required i will buy, there are some Chinese products with full range in the 300$ price and some good reviews in this forum.

For example if in the lows i have this range of frequencies: 33hz, 55hz, 80Hz, 120Hz, 250Hz, 400Hz

So, do i need a LCR meter that can test in all the range of frequencies that i am working with in the eq cutoff?

Ps: I asked this same question to ChatGPT, i got a response:

Yes, you need a full range LCR meter to test all your components in that frequencies...not sure at all, i'm just a noob in electronics.

Best Regards!

[Benta]

Dunno the thing, but I highly doubt that the inductors are "2H, 1H, 400H etc.".

[kryz]

Well i had an error typo in the 400H was 400mH edited already!

I just posted very approximate values the real ones for one of the multi tapped coils are:

2H, 1.1H, 450mH

[TimFox]

Lacking an LCR meter, you can make an easy parallel-resonant circuit with a known capacitor.
The parallel-resonant frequency can be measured by connecting a signal generator (with frequency counter) through a large resistance to the L-C parallel circuit, monitoring the output with an AC meter or oscilloscope with a high impedance input, looking for peak response.
Choose the capacitor value to get a relatively low resonant frequency with your guess of the inductance:  this relatively high capacitor value reduces the effect of stray capacitance in the test circuit.
Capacitors with 1% manufacturer's tolerance are readily available:  what precision do you need?
I agree with Benta about the doubtful inductor values:  do you mean mH?

[kryz]

That answer looks so interesting for practicing, i do have an oscilloscope and a signal generator so i can do that circuit.

In my studies i am now in the electromagnetic section, the next chapters are Capacitors, next AC, so you know the level i have....Kirchoff, ohm law and for now the Lenz law.

The point is i am retiring to a place that i won't have access to buy tools and very little internet, is a remote island where i used to live before, and i'd like to have all the tools required to study and practice before i go there...not even ebay, amazon, etc.

I am just learning about LC filters for now passive ones and doing a lot of maths required in the book, so i don't know really the precision that i need i guess the most the best.

These coils are very old style ones,  so those big values, are hand made by don audio, people don't use those actually they are more in gyrator emulation of coils with opamps.

The inductor is:

DAEF530 Neve T1530 EQ Inductor - 2H, 1.1H, 450mH

[kryz]

Also as i understand in the book, the theory will be one and when i mount the circuit the inductance created by the wires and other components will affect it.

So i think i need some LCR meter that i can test in circuit with low voltage values to don't stress the components, this is all i know watching videos in youtube....

[Benta]

To be honest, I've worked with inductors myself and have never had use for an LCR meter. Their use is too limited in range and frequency range.
Multimeter: yes
Oscilloscope: hell, yes.
Function generator: yes.
Lab power supply: yes.
With those I can do 99% of the measurements I need.
In your case, I'd shop around for a couple of old-fashioned capacitor-decade boxes (like the physics lab in school) in the nF/uF range and do what TimFox suggested.

[DrGeoff]

Dunno the thing, but I highly doubt that the inductors are "2H, 1H, 400H etc.".

Yes, the Neve EQ circuit use 2H and 1H coils. The 1084 has a 10H coil.
I've always used a known reference capacitor (I have a set of precision caps that I use for this) in parallel and either use a scope in x-y (current/voltage) looking for the in-phase frequency as it is swept, or an AC millivoltmeter looking for the dip and measuring the minimum value and the frequency at which this value is 3dB higher on each side, and then use the centre between these two frequencies as the resonant point.

[kryz]

Well as i see the LCR meter is not really needed or the cheap ones won't help so much more with the limited fixed frequencies, even i liked that it calculate some interesting values automatically, anyways maths will do mostly the work.

Thanks for enlightening me, i have to study more anyways to put in practice all the theory of the book and understand well all, i just thought maybe LCR meter will help me to calculate on circuit some values easily.

Anyways as Benta said i have the most important tools  and they are enough even in a remote island, those tools, books, and study will gave me the results that i need.

This week will arrive the inductors and will be time to study, practice and check the things that i have in mind.

All the best,

[Benta]

For your application, I'd add the decade box all the same. Example:
https://www.tequipment.net/Extech380405.asp?v=7324
That covers the range you'll be working in.

Apart from that, Good Luck on your Robinson Crusoe island

[kryz]

I want you know that i began to study seriously just 1 month ago, i mean the maths, i have an idea of what the components do, so some of the answers were even hard to understand, i had to review my book again and again i have the theory very very fresh in my mind.

For example i didn't know what's a decade box 

This book is all maths 800 problems to solve, not so much into examples of practical circuits, better said nothing practical in this book.

I was looking now for the decades box...quite expensive i see they are about 200 euros, minimum.

If i understood well they are a box with many values of capacitors with good precision, i guess i can build myself one buying good precision caps.

I am a software developer, a bit old school so i had to work with some pics and assembly and i had to touch some basic electronics in my life, very basics.

No problem with digital signals but analog circuits was always something that i liked to study, i always study never stopped, my mind is so crazy.

But i have to learn to walk before run like always was and i know will be a long and exciting way.

Thanks for saving me 300 Euros i was almost going to buy it today.

My island is so nice and quite, white beaches and still a bit of internet and enough to maybe ask some more questions here 

I will avoid some more recommendations of the ChatGPT IA at least concerning to buy equipment 

Best regards!

[Benta]

A decade box is simply a variable capacitor controlled by switches, nothing else. It's fast and neat, but if you have a good collection of capacitors, you can achieve the same by soldering together appropriate sized to get the desired value.

[David Hess]

To be honest, I've worked with inductors myself and have never had use for an LCR meter. Their use is too limited in range and frequency range.

I finally bought an DE-5000, but for decades got by with either an impedance bridge or nothing.  For testing power inductors, I get more useful results by applying a fixed voltage and measuring the current rise which will show the saturation point and how sharp it is.

A network analyzer would be useful for measuring impedance over a wide range of frequencies, but I have never found one worth spending real money on.

[Benta]

For power inductors, itcan get complicated as there often is a DC component as well.
30 years ago, I made myself a small current transformer on a ferrite toroid (~15 mm OD), 100 windings. I still have it and use it, often for in-circuit measurements. Wire through the hole, that's all.
I use it mostly for di/dt measurements with a square wave applied to the inductor to be measured, the slopes of the triangular wave gives a good indication of inductance (if it's not triangular, there's a saturation problem.

[jonpaul]

Kryz, bravo for your efforts to learn about electronics

videos, chat gpt, or even this forum may not be the best information.

Many fine books and papers on audio filters, EQ, and filter designs.

since 1970s active filters without inductor are used.

Nowadays the filters are digital.

For audio equalizer, speaker crossover etc, an audio, home cinéma forum is better.

I would delay any equipment purchase till you can learn more.

Finally look for a ham radio flea market for parts and instruments

jon

[kryz]

Thanks Jonpaul for your recommendations.

I am really following one book is called in spanish "Electrotecnia" i think the first part of this book is common for all the electronics.

But it is a bit in the side of mechanical applications; How one motor works, 3 phases ac, lighting, i like it because is interesting to know how a motor works, but i like more digital and audio. apps.

So sometimes a complement my studies with some videos about audio in youtube, there are some great videos about tubes and amplifiers very very well explained, Uncle Doug has some great videos.

Chat GPT: Really i just talk once with it, i don't use it anymore, i was just curios about it, anyways i think is another resource to have and for now is free at least until IA get the world control...joking.

About buying equipment is hard when you don't know the specs or what you need, i was in the cheap side for a while, but i realize sometimes the cheap is more expensive, when you have to buy again the same tool because the cheap is not useful anymore, i do have the basics for now:

-Rigol cheapest scope.
-Signal generator.
-Some chinesse multi meters and component tester.
-Power dc, very nice one and quite.
-Iron

But none of them can measure inductors, even i can measure with the scope and some formula, maybe i'd like to can measure fast so i was in the LCR searching, also i saw they give you some very nice values as the Q and ESR which for what i know they are very useful.

I have many electronic books in the list, but i am sure i won't understand anything unless i have the base, maybe someone is interested so i list the books that i collected  in my research for audio and generics:

-The Art of Electronics.

-Troubleshooting analog circuits.

-Small signal audio design.

-The Audio Cyclopedia.

-Steve Dove Console design.

-Introduction to audio signal processing.

I am returning 30 years back when i was so exciting with programming and discovering many new things every day, math is really challenging in electronics, sometimes i get stuck in some problem for hours.

Best Regards,
Kryz