Re: Variable Capacitance and Inductance

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Barton B. Anderson by way of Terry Fritz <twftesla-at-qwest-dot-net>" <tesla123-at-pacbell-dot-net>

Hi Dave,

I made a temperature  test today on a small coil (1" x 5"). Inductance
measured before any temp
change was 405uH and unchanging on the meter. Using hair dryer I measured
407uH stable. As I let it
cool, it dropped back down - stable. I then put it in the freezer for a
little while. Measured
411uH. It went back to 405uH at room temp. Capacitance couldn't be measured
by the meter.

Thermal expansion as Terry mentioned is all I'm saying. Temp changes both L
and C because the
object physically changes - this should be easily understood. Also, the
amount of changes depends
on the L and C value based on the objects size and amount of physical
change. Usually, pretty
small.

Humidity affects walls and other objects which can become greatly more
conductive in humid
conditions. If the walls or whatever is conductive or significantly changed
in conductance by water
saturation, you're not going to see a defining change. As far as that goes,
the object itself isn't
what is changing, but the capacitive affects of objects to test object (not
the test object itself
unless the environment causes a physical change). The proximity has much to
do with how much change
you will measure. A huge coil in a small bath room will show a greater
change than a small coil in
the same bathroom (capacitive affects). That's all I'm saying. This is
known - has been known a
long time. We see this change occur all the time. If Tesla was discussing
vibration, then he is
discussing frequency measurements we know changes with proximity to
external conductive objects.

Take care,
Bart


Tesla list wrote:

> Original poster: "David Thomson by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <dave-at-volantis-dot-org>
>
> Hi Bart,
>
> Thanks for pointing out the transformer error.  It's important to know about
> errors.  Especially for measurements off by the magnitude you were showing.
>
> Have you tried putting a hair dryer to your coil to see if temperature
> affects it?  Even with a 100 degree temperature variation, I had no
> inductance variation.  I'm going to put my coil in the shower today to see
> how humidity affects it.  I'd like to know for sure whether temperature or
> humidity are directly responsible for variations in coil inductance.
>
> Dave