Re: MMC dissipation factor measurement

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

Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>


Could one measure dissipation with a calorimeter?

That is, put a known RF power through the cap, which would be immersed in a
well stirred oil bath in a vacuum bottle (thermos) (or even a suitable
styrofoam container might work).  You'd measure, accurately, the
temperature over time.

Say you could put 100W through the cap.  If the dissipation factor were,
say, 1E-4, that would result in 10 mW being dissipated in the cap.  Run it
for 1000 seconds (about 20 min), and you've put 10 joules into the system.
Say the whole thing (oil and all) had a mass of 50 g.. insulating oil at
60C is about 2.09 J/gK.. So, you'd expect a temperature rise of around 0.1
degree...

If you put it in some low boiling liquid (LN2?) you might be able to
measure the volume of gas boiled off, and use the heat of vaporization.



Tesla list wrote:
> 
> Original poster: "Malcolm Watts by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>
> 
> Hi Terry,
> 
> On 16 May 2002, at 21:13, Tesla list wrote:
> 
> > Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>
> >
> > Hi All,
> >
> > The question comes to me tonight....
> >
> > I have a TEK 3012 scope.  I have a TEK 5100 voltage probe, lots of Pearson
> > current monitor CTs...  I have a lot of sine wave generators with low
> > impedance...  Like 350kHZ at 5 amps...
> >
> > So, would I have any chance "in the hot place" of measuring the dissipation
> > factor of a poly MMC cap?  Like <0.001 dissipation factor...
> >
> > I guess I would have to detect the difference between 90 degrees and
> > 89.87856 degrees to find the dissipation factor...
> >
> > Sounds doable but maybe someone out there has "been there, done that..."  I
> > was just asked the question and "I" have not thought much on it cause I am
> > sleepy :o)  Might need a step down transformer to get a really low source
> Z....
> >
> > Cheers,
> >
> >       Terry
> 
> You may be able to do it on an incremental basis using bridge
> techniques. I am suggesting measuring the difference between two
> different types of capacitor, the one with the lowest esr score then
> going on to be the standard for a succeeding test which compares
> another. Hazy I know.
> 
> Regards,
> Malcolm