Re: quick mmc cap. question

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

Original poster: "Terry Fritz" <teslalist-at-qwest-dot-net>

Hi Mark,

At 10:11 PM 3/3/2003 -0600, you wrote:
>>>I think you need a few work benches!  :)
>>
>>Ya.  Getting to old to play on the floor ;-))
>
>And I would imagine it gets a little hard on the back and knees, 
>too.  Even at my age (almost 25), I find it hard to sit and work on a 
>stool or floor.
>Then again, bad knees and back (arthritis) runs in both sides of my 
>family. . . .

At 40+, I find getting on the hands and knees is great excersize.  Keeps me 
flexible.  Of course, I have 50 square feet of bench space in that room 
too, but it is piled up with junk :o)))



>>>That works out to 10.5A for a 15C rise (same as the .15uF cap test) - 
>>>definately excellent, IMO!

Almost "too good"??  I "think" I did things right so I am guessing CD has a 
new low ESR trick.


>>Yes!!  Perhaps these caps have more surface area or something.  They seem 
>>to have VERY low ESR!!  Maybe CD figured something out.
>
>Yes, and I wonder if maybe the .15uF caps have been improved, too?  Should 
>we send you another sample or three of the bigger ones, perhaps?

I really only need 'one'.  I am getting better at not destroying them now ;-))


>I'm curious as to how you measure a 1.03C temp difference, and what the 
>accuracy is on that measurement.

I just use a K type thermal couple thing I got from Sears automotive and a 
4.5 digit DVM.  Seems perfectly stable and has the basic "precision" 
needed.  Absolute accuracy seems great too as far as I can tell.  I have 
the 6.5 digit HP too but I hate to connect it to things that might 
potentially blow up ;-))  I put things in an plastic tube with plugs on the 
end to stabilize the temperature.

>Were (are) you shooting for some current value, or temp rise?

The current is just the most the generator can do within the 250 watt 
reflected power limit.  It has an output matching transformer and such.  I 
play with things to pump as much current as possible and then I see how hot 
that current makes the cap.

It takes a long time for the cap to get to a stable temperature, but the 
basement here is really stable.  I then turn on the generator for 15 
minutes and see what the temperature rise is.  I tape the thermal couple 
probe to the cap body with a bunch of electrical tape.  1 degree C is a 
pretty small temperature change so precision suffers.  But that is what the 
results are...

>The more I think about your testing, the more inquisitive I become!  I 
>also like to learn which are the arbitrarily chosen variables in a 
>test/design, and which were defined by a goal or constraint.

The generator does 350kHz, 900 watts forward, 250 watts reflected power 
into 50 ohms.  Extreme accuracy.  I just have to present a load to the 
generator where it does the most current and measure the temperature 
rise.  It is all in the trick of feeding the generator with an RF load it 
likes with the cap in series.  Here is a big pic with labels.

http://hot-streamer-dot-com/temp/P3020007a.jpg

I'll pass this to the whole list too for everyone's entertainment.  just to 
show I really don't just make these numbers up ;-))

Cheers,

         Terry


>Thanks,
>
>Mark Broker