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Default AADE inductance measurement not trustworthy

Another degaussing coil, this one from a large TV.
21 inch diameter, kinks minimized.
AADE measures 9.11mH.
One of those "universal" kits that measures almost anything reads
16.8 ohms, 2.55mH.
Using a 0.1uF cap in parallel and driving that with square wave and
10K in series, rings at 9.5KC for 2.8mH
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Default AADE inductance measurement not trustworthy

On Thu, 14 May 2015 02:23:23 -0700, Robert Baer
wrote:

Another degaussing coil, this one from a large TV.
21 inch diameter, kinks minimized.
AADE measures 9.11mH.
One of those "universal" kits that measures almost anything reads
16.8 ohms, 2.55mH.
Using a 0.1uF cap in parallel and driving that with square wave and
10K in series, rings at 9.5KC for 2.8mH


DEGAUSSING coil? Still living in the past?

Here we have 5 flat-screen TV's, 3 flat-screen monitors, 1 flat-screen
O'scope and only one very ancient O'scope with a CRT.


...Jim Thompson
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| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.
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Default AADE inductance measurement not trustworthy

On Thu, 14 May 2015 02:23:23 -0700, Robert Baer
wrote:

Another degaussing coil, this one from a large TV.
21 inch diameter, kinks minimized.
AADE measures 9.11mH.
One of those "universal" kits that measures almost anything reads
16.8 ohms, 2.55mH.
Using a 0.1uF cap in parallel and driving that with square wave and
10K in series, rings at 9.5KC for 2.8mH


There's probably a lot of distributed capacitance in that coil. Can
you measure the coil SRF?

The AADE is an oscillator that runs at a fairly high but variable
frequency. It's great for small Ls and Cs, not so good for bigger
stuff.


--

John Larkin Highland Technology, Inc
picosecond timing laser drivers and controllers

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

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Default AADE inductance measurement not trustworthy

Jim Thompson wrote:
On Thu, 14 May 2015 02:23:23 -0700, Robert Baer
wrote:

Another degaussing coil, this one from a large TV.
21 inch diameter, kinks minimized.
AADE measures 9.11mH.
One of those "universal" kits that measures almost anything reads
16.8 ohms, 2.55mH.
Using a 0.1uF cap in parallel and driving that with square wave and
10K in series, rings at 9.5KC for 2.8mH


DEGAUSSING coil? Still living in the past?

Here we have 5 flat-screen TV's, 3 flat-screen monitors, 1 flat-screen
O'scope and only one very ancient O'scope with a CRT.


...Jim Thompson

NOT relevant to problem seen.

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Default AADE inductance measurement not trustworthy

John Larkin wrote:
On Thu, 14 May 2015 02:23:23 -0700, Robert Baer
wrote:

Another degaussing coil, this one from a large TV.
21 inch diameter, kinks minimized.
AADE measures 9.11mH.
One of those "universal" kits that measures almost anything reads
16.8 ohms, 2.55mH.
Using a 0.1uF cap in parallel and driving that with square wave and
10K in series, rings at 9.5KC for 2.8mH


There's probably a lot of distributed capacitance in that coil. Can
you measure the coil SRF?

The AADE is an oscillator that runs at a fairly high but variable
frequency. It's great for small Ls and Cs, not so good for bigger
stuff.


80KC.



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Default AADE inductance measurement not trustworthy

Robert Baer wrote:

Another degaussing coil, this one from a large TV.
21 inch diameter, kinks minimized.
AADE measures 9.11mH.
One of those "universal" kits that measures almost anything reads
16.8 ohms, 2.55mH.
Using a 0.1uF cap in parallel and driving that with square wave and
10K in series, rings at 9.5KC for 2.8mH

First, something like that will be affected by anything within FEET of the
coil. So, if you moved the coil to hook it to the instrument, the reading
could change.

Second, I see you state the test frequency is 80 KHz, with a bunch of close-
packed turns in a big coil like that, the parasitic capacitance is goign to
be a LOT, which might throw off some measuring instruments. A good bridge
should take that in stride, but some simple instruments might be fooled.

Jon
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Default AADE inductance measurement not trustworthy

Jon Elson wrote:
Robert Baer wrote:

Another degaussing coil, this one from a large TV.
21 inch diameter, kinks minimized.
AADE measures 9.11mH.
One of those "universal" kits that measures almost anything reads
16.8 ohms, 2.55mH.
Using a 0.1uF cap in parallel and driving that with square wave and
10K in series, rings at 9.5KC for 2.8mH

First, something like that will be affected by anything within FEET of the
coil. So, if you moved the coil to hook it to the instrument, the reading
could change.

Second, I see you state the test frequency is 80 KHz, with a bunch of close-
packed turns in a big coil like that, the parasitic capacitance is goign to
be a LOT, which might throw off some measuring instruments. A good bridge
should take that in stride, but some simple instruments might be fooled.

Jon

NOT "test frequency"; the Self Resonant Frequency.
No measuring instrument is going to be "thrown off".
The observed SRF DOES change a bit when moving the coil around,
particularly from vertical to horizontal axis (where coupling to rack
equipment can be larger).



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