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How Do I determine the Toroid Type of some mystery roids I found while dumpster diving??????

Thu, 11/19/2009 - 08:23 — wb8icn

From one of the QRP reflectors:

 

"Well, either these roids are special order and I have no idea what they are made of...or I am doing something very wrong.

I wound 20 turns and measured: uH = 15.65uH. Then I did this for 15, then 10 and finally 5 turns.
20 turns = 15.65uH
15 turns = 9.83uH
10 turns = 5.70uH
5 turns = 2.02uH

Then I took that data and stuck them into the formula uH = (Al * (Turns * Turns)) / 1000. By rearrangement, Al = (uH * 1000) / (turns) * (turns). This gave me the following:
20 turns = 15.65uH, Al = 39.125
15 turns = 9.83uH, Al = 43.69
10 turns = 5.70uH, Al = 57.00
5 turns = 2.02uH, Al = 80.80
I knew something was wrong after doing the second Al value since the Al value should not change when I change the number of turns on the toroid.

Any help for a very confused old guy???????

72/73....Mikey, WB8ICN"

If anyone knows how to determine what type a toroid is, please let me know. wb8icn@gmail.com or post a reply here!

 

Comments

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Tue, 12/15/2009 - 14:31 — wb8icn

Measuring Roids Properly...

I sort of got sidetracked from my experiments. I will make sure I have more consistant core coverage and cover at least three quarters of the core no matter the number of windings.

I thank everyone for their comments and suggestions.

 

72's....Mikey, WB8ICN

—

72's/73's...Mikey, WB8ICN

www.qsl.net/wb8icn

Fri, 12/11/2009 - 18:33 — Scotman

Measurement of toroid Al

Mikey.

I did a series of measurements on a T68-6 core. In each case the windings were spread over approximately 270 degrees. The results, which were pretty consistent, were as follows:-

1. 26 turns = 3.873 microhenries = 5.72 Al 

2. 20 turns = 2.402 microhenries = 6.00 Al

3. 14 turns = 1.171 microhenries = 5.97 Al

4. 8   turns = 0.449 microhenries = 7.02 Al

When I "bunched up" the 8 turn winding, the inductance increased to 0.768 microhenries, a whopping 71% increase, and a calculated Al of 12. So, obviously when doing these kinda measurements, the spacing of the winding is important. I suspect if you repeat your measurements with equal core coverage by the windings you may get different, and maybe more consistent results.

Measurements were made with my trusty AADE LC meter. I should also point out a little quirk with Al figures. Al is normally measured in nanoohenries/(100 x 100). Amidon, however, quotes Al in microhenries/100. In other words THEIR Al appears to be 10 times as great as everyone elses :-)

In any case it looks like you have either a 61 or perhaps a 43 type ferrite

Hope this helps

Ned, KD8FCB   aka Scotman

Thu, 12/10/2009 - 20:00 — nald

Toroid Type

The Toroid type high-pressure device and its predecessor, the
Chechevitsa (lentil) type high-pressure device, are known to be used
efficiently for the synthesis of new materials in recent decades. It
was through the Chechevitsa device the first ultradense modification of
silica, 'stishovite', was obtained. Both devices were essential for the
industrial production of superhard materials in the USSR and other
socialist countries. In 1980s, almost half of the world synthetic
diamond and c-BN products were manufactured by these devices. see essay for more detail....

Sun, 11/22/2009 - 17:32 — AD7EV

measuring toroids

What method are you using to measure the the inductance.  An RLC bridge or digital inductance meter will likely not work well. You should make a good guess at the frequency range, find a nice stable cap, dip the resonant circuit and then calculate the inductance.  My HP RLC bridge uses a audio frequency to drive the bridge, and the results with RF components are marginal at best.  Your AL numbers seem to be in an appropriate range for something like a 61 mix ferrite.  Make sure that the number of turns is spread over the same angle of the core.  It seems that spreading the turns over 270 degrees was recommended somewhere.  It has been many years since I coverd anything about magnetics in college, but I would expect some variation in AL as more turns were added, but I would expect that variation to have a consistent direction.  ALSO.....  Amidon always had a disclaimer about actual number of turns may be different ..blah blah, so I expect they were covering for some expected core to core variation.  It would be interesting to know the variation between the cores if they are say all 10 turns.

I have to evaluate a bunch of cores here in a month or so when I get ready to start a switching regulator project, so I'll get to see if my advice is any good at that time.  My take is that you may be ok in your measurements, and using a more accurate method, or determining core to core variation may clear everything up.

john  AD7EV