Re: Simple way to measure inductance?

On Sun, 05 Feb 2006 15:05:34 GMT, Rich Webb
<bbew.ar@xxxxxxxxxxxxxxxxxx> wrote:

On Sun, 5 Feb 2006 02:52:17 -0600, "Abstract Dissonance"
<Abstract.Dissonance.hotmail.com> wrote:

"Bob Monsen" <rcsurname@xxxxxxxxxxx> wrote in message
news:pan.2006.02.05.08.10.53.928384@xxxxxxxxxxxxxx
[snip...snip...]
You could also buy one of these:

http://www.aade.com/lcmeter.htm

naw... I don't need to spend that kinda money on something I probably won't
use much and that I might be able to make on my own(to a good enough
approximation to satisfy my needs). I'd rather spend the money on the
components and try to make my own and screw up but learn something.

I put together one of those LC meters also and agree with Bob that
they're a pretty good value for a home shop.

For one-off measurements, if you have a signal generator, frequency
counter, and o-scope you can use a simple bandpass layout to get the
value of the inductor. Vary the frequency to peak the output; at the
peak Zc = Zi.

___ ___
Input| \_------|___|-----------. measure here
here |___/ |
|
.---o---.
| |
| |
--- C|
--- C|
| C|
| |
'---o---'
|
|
===
GND

---
Using a series-resonant circuit, you'll get a better peak if you do
it like this:

INPUT----+
|
[C]
|
+---->>---+
| |
[L] [DET]
| |
GND------+---->>---+

Where the impedance of DET at resonance is >> than Xl at the
frequency of interest,


Or a suck-out if you do it like this:

INPUT--[R]--+---->>---+
| |
[C] |
| |
| [DET]
| |
[L] |
| |
GND---------+---->>---+

Where the impedance of the detector becomes less critical.

--
John Fields
Professional Circuit Designer
.