something VERY WEIRD and re to Re: actual measurements & pictures of the TC in action
Terry, thanks for the reply. So then was it sheer luck that my DMM came
so close to what wintesla predicted for Lp? Supposedly the range of the
27x for L is low enough to accurately measure the primary L. Certainly
the other info explains the other readings I got that didn't make
sense. Wish I had a couple G's to plunk down on a scope and the like :(
I was shocked by the EMMC reading as well! I will keep a close eye on
this value. I ran my coil today for 30 minutes with very little rest
time and the caps are still great! I am even running my gap a little
wider than will normally fire with just the NST in the circuit...which I
assume means the caps are seeing a little more than the 12kV rating of
While I'm talking about weird things, I had something REALLY weird
happen today. I am running my gap across my NST. The wire from the one
end of my EMMC to the primary was 10 AWG. I had some 8 lying around and
decided to see if it would make any noticable difference. So I replaced
the 10 gauge wire with 8, of exactly the same length. I routed it as
close to how the old one was as possible. When I fired up my coil,
spark length started at a puny 8-10" and immediately dropped to tiny
little ones less than .5" long. Of course this happened before with my
two-bolt gap, but my newer gap has shown no signs of that, even after 5
or longer minute runs. I let the coil sit a while, came back, and still
the same. I then immediately replaced the 8 gauge with the old 10, and
voila, back to the old performance. While the "problem" was easily
fixed, its cause has me super curious. Any thoughts?
Tesla List wrote:
> Original Poster: Terry Fritz <twftesla-at-uswest-dot-net>
> Hi Stan,
> Some of these measurements need special or sensitive equipment to
> are beyond the meter's ability to measure.
> Primary Inductance - This inductance is usually so small that it falls at
> the edge of most simple meter ranges. The best way to measure Lp is to use
> an oscilloscope, sine wave generator, and frequency counter. A known
> capacitance is placed across the primary (like the primary cap) and the
> resonant frequency is found and the values are back calculated from there.
> This method can easily get the correct value to less than 1% error.
> Primary Wiring - a piece of wire has inductance and capacitance. However
> these values are far below what you meter can measure. The capacitance is
> on the order of 1pF and the inductance may be around 50nH. These values
> are usually so small than can be ignored.
> Secondary Inductance - Your meter should be able to easily and accurately
> measure this.
> Cself - Cself needs to be measured with the scope, signal generator, and
> counter setup mentioned above. It is very sensitive to the surrounding
> objects and is known to be tricky to measure accurately.
> Ctoroid - Like Cself, it needs the special equipment but the measurement is
> far more stable and easy to do accurately.
> Csparkgap - Your meter probably can measure this just fine.
> Cnst sec-gnd - Your meter can measure this.
> Rnst - secondary - Your meter can very easily measure this.
> Lnst primary - You cannot measure the inductance of an iron core
> transformer with a simple battery powered meter. The transformer core
> needs a substantial current (around 1/4 amp) at near the rated frequency
> for the core to magnetize properly. However you can measure this. With
> nothing connected to the output of the neon, find the no load current draw
> of the AC input at the rated voltage.
> Lp = Vin / (2 x pi x F x Iin)
> In most cases, the fancy programs are very good at predicting all these
> values. They are usually within 5%. After seeing how difficult some of
> those values are to really measure, you can see why these programs are so
> I am very surprised that your EMMC went UP in value! I have no exlanation
> for this....
> At 01:04 AM 8/6/99 -0400, you wrote:
> >I measured my EMMC of 2 strings of 10 of the panasonic 1600V .056u at an
> >actual 11.16 nF. That is UP(!) from right after its construction before
> >its first use. Then it was 11.13nF.
> >I also measured everything else I could clip my little meter leads to
> > Measured Wintesla
> >Primary .012mH .0179
> >Pri & wiring .016mh NA
> >Secondary 7.8 mH 7.6
> >Cself 62pF 7.10pF
> >Ctoroid 86pF 21.4pf
> >Csparkgap .048nF NA
> >C nst sec-gnd .038nF
> >R nst second 5.95kO
> >L nst primary 34.1mH
> >DMM is a wavetek 27x and all values are adjusted from base reference.
> >It looks like wintesla was VERY close on primary and secondary L, but
> >either my meter won't go low enough or wintesla was wrong on the C's.
> >Has anyone else measured this stuff? Do my other measured values look
> >I finally got off my lazy butt and took some pics of my coil in
> >operation. It's so easy to take non-operating pics with a digital cam
> >that I have film cam motivation problems! Anyway, I used a $100 Pentax
> >K1000 with manual everything, a pentax 35mm 2-22 f-stop lens, a $20
> >tripod, f stop at 4, shutter on bulb. I ended up with the best combo at
> >4 seconds. I used crappy Fuji 800 ISO film. Anyway, more info, along
> >with the pics, is posted on my site. http://tesla.better-dot-org/sgd
> >I think my coil is simply not bright enough to have a chance of getting
> >away with 100 or 50 ISO. Shutter time would have to be around 12
> >seconds or more and I'm already getting too many sparks for my taste.
> >Next project is to set up the ol' camcorder then run the tape through my
> >cap card and make some AVIs.
> >Incidently, I accidently left my Kodak DC120 digital cam in the room
> >while doing the manual pics and it was fine. It was about 8' away and
> >probably saw a total of 4 minutes of the TC being on.