I see that AADE is closed; one-man shop, he is sick as all heck. I need a repair or replace as my meter, when reading 22mH/88mH inductors is (as many know) unreliable (to be polite). All cap scales seem to be reliable and repeatable.
Help? (thanks in advance).
If anyone has an AADE meter and some 88mH inductors could you check and see if you have consistent, reliable and repeatable readings? I wonder is it low drive causing the problem? Could it be the frequency of measurement, I think with an 88mH you're AADE oscillates around 22KHz and 22mH is 40 kHz. What is the SRF of the 88mH inductors? 22mH inductors?
Mikek
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Perhaps try with a function generator and a scope and measure it "old school" and see if the results match and are repeatable
Cheers
Klaus
I did a long search to find the SRF of 88mH telco inductors without any success. Anyone have one to test? Mikek
Pity. He ran a great operation.
Why would anyone want to measure the inductance of an 88 mH inductor?
But seriously, the AADE is not reliable with big iron core inductors. Few simple LC meters are.
As Klaus says, measure it some other way.
If you have a 50 ohm function generator and a scope, you can use a square wave to measure the L/R time constant, or a sine wave to find the 3 dB point. And the scope displays saturation distortion, if any.
You can also resonate it with a capacitor, shooting for something close to your intended operating frequency.
-- John Larkin Highland Technology, Inc picosecond timing laser drivers and controllers jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
An i gave away a homebrew Owens bridge...
What type of inductors are they?
"L/C Meter IIB will NOT measure inductors designed for 60 or 120 Hz applications such as power transformers, filter chokes or motors. The minimum test frequency is about 20KHz and these devices have enormous core losses at that frequency."
These inductors were used by the phones company as loading coils. Here's as much as I know,
Mikek
Robert, can you run a self resonant frequency test on one of your
88 mH coils? I've done a pretty good search and have not found the info. I did find a guy that had 2,500 coils back in 2007. MikekOn a sunny day (Sat, 13 Dec 2014 12:41:10 -0800) it happened Robert Baer wrote in :
Robert if that hing works the same way as my cap/inductance meter
You could use a test circuit with for example a JFET as oscillator, and use a frequency counter, and make sure it oscillates at a much lower frequecy (much bigger cap values, say 100nF), and calculate L from that.
Also for large powder cores any magnetic field nearby will saturate the core and cause a lower L to be calculated.
telephone audio, about 300 to 3000 Hz. The test frequency is in such range that the core losses spoil the measurement.
The idea with the coils was to add inductance to an open-wire telephone line to increase its characteristic impedance and so decrease the attenuation from the wire resistance.
-- -TV
When the measurement is made above or close to the self resonance of the inductor, you really just measure loss or primarily shunt capacitance
Measure the inductor at several frequencies and plot it. The assumtope should be resonable straight
Cheers
Klaus
Powdered ferrite? Those loading coils were usually powdered iron or, if you're lucky, powdered permalloy.
Is there powdered ferrite?
-- John Larkin Highland Technology, Inc picosecond timing laser drivers and controllers jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Thanks! In my day as they say,they were used in RTTY work; the one there is the bifilar version;the other version is "split" winding, pro on left half,sec on right half with a cardboard-like barrier in between as if the barrier itself was a one-turn winding. Explains why i got similar high calculated inductance (130mH instead of the design 88mH) with RL scheme at various frequencies.
Yes there is; i think of any core that seems to be powdered as "powdered ferrite".
Do you call your fancy china "powdered clay"?
They're the same thing: a fully sintered, rigid, inorganic ceramic. Nothing powdery about [as-manufactured] ferrite at all.
Tim
-- Seven Transistor Labs Electrical Engineering Consultation Website: http://seventransistorlabs.com
The Piconics super-wideband spiral inductors are filled with ferrite-powder-loaded epoxy. I guess there are powdered ferrite inductors, but most low-frequency signal-level toroids are powdered iron or powdered permalloy, with a distributed air gap. I think.
The permalloy is great: high Q, lots of energy storage, relatively expensive. Kool-Mu gets close.
-- John Larkin Highland Technology, Inc picosecond timing laser drivers and controllers jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
On Tue, 16 Dec 2014 07:26:19 -0800, John Larkin Gave us:
Inexpensive? oops.
Permalloy is expensive, compared to powdered iron. Worth it for some apps. The Kool-Mu is close in performance for power apps but cheaper than permalloy. I've burned the paint off Micrometals powdered iron cores in switchers, and a Kool-Mu core saved my cookies.
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
They were used in ham RTTY decoders, after they were available from telco surplus. It was an easy way to make tuned circuits for 2125 Hz and
2295 Hz (for FSK mark and space) in the tube era.Been there, done that, 50-odd years ago.
-- Tauno Voipio
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