[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [TSSP] Ion Cloud Loading
Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>
Cross posting a bit...
I suddenly found as I walked out the door for work this morning that the whole
town was socked in with snow. Weee!! Snow Day!! :-))))
I think the output impedances of the TCT and Bertan really killed the Q of the
other test so I set it up differently.
I set up the secondary driven from the HP33120a (Zout = 50 ohms, I could have
used a low-z amp but I forgot) with the Tek3012 monitoring the signal with the
antenna as is normally done. I set a second coil and terminal next to the
first and charged them up with the Bertan:
http://hot-streamer-dot-com/TeslaCoils/Misc/IonCloudTest/NextTest.jpg
The center and -3dB frequencies are:
263.84kHz
262.00kHz
260.30kHz
Thus the Q is 74.86. I set the signal to 9.00 volts (I must have moved because
it was 9.04 when I started the test) giving a resolution of 1 part in 900. I
could detect the Fo frequency change 140Hz in this way or 1 part in 1870. So
charging the right sphere up from 0 to 45 kVDC gave the following shift in the
received RMS signal.
kVDC Voltage
0 9.04
5 9.04
10 9.04
15 9.04
20 9.04
25 9.04
30 9.04
35 9.04
40 9.04
45 9.04 (corona)
So having the coil close to a charged object seems to have no effect on the Fo
frequency. If there is some tiny effect down there in the noise, it would not
be detectable in normal situations unless something goes wildly non-linear at
really high voltages.
-------------
Just a little follow up. I hooked up the lowZ amp which raised the Q to
79.66 and set the frequency offset a bit were a small change in Fo made a
big change in voltage. I could detect a shift in Fo of only 5Hz this way!
I reran the test (I could not move without affecting the test) and still
saw zero shift in the Fo frequency caused by the voltage on the left (not
right as I said in the last post) sphere. Of course, I could hook up the 7
digit HP meter in place of the scope but the background noise is now the
factor rather than being able to measure close enough... I would need a
copper shielded room to go further, but I think Malcolm's question has been
answered ;-))
-------------
One could always false streamer load a cold coil. Just bend a piece of
wire in the shape of a streamer and hook it to the top terminal to see how
much the "wire streamer" changes the tuning. The wire should have very
comparable added capacitance effects to those of a real streamer. This may
be a way of predicting streamer loading for coil testing or tuning if one
were really that concerned. One may be able to add say 220000 ohms of
resistance to ground to simulate the drop in Q of the coil too (maybe add
the resistance at the coil's base). Perhaps a simulated streamer load
bent out of piano wire would be a useful test tool to have around...
Cheers,
Terry
At 10:53 AM 3/1/2002 -0800, you wrote:
>Excellent experiment....
>
>
>Another experiment would be to attach a thin wire a meter or so long to the
>topload (to replicate a "leader" or spark channel) You could use nichrome
>to give it some resistance... Hang it with monofilament
>
>
>Tesla list wrote:
>>
>> Original poster: "Terrell W. Fritz by way of Terry Fritz
><twftesla-at-qwest-dot-net>" <terrellf-at-qwest-dot-net>
>>
>> Hi Malcolm,
>>
>> I seem to have more than enough equipment to do this (almost an obscene
>> amount in fact ;-))
>>
>> I set up my 0-50kVDC Bertan X-ray power supply and my little battery
>> powered (and cheap if something goes wrong) TCT Tesla Coil Tuner (a simple
>> adjustable square wave generator) in series between ground and the coils
>> base connection:
>>
>> http://hot-streamer-dot-com/TeslaCoils/Misc/IonCloudTest/HVDCPower.jpg
>>
>> http://hot-streamer-dot-com/TeslaCoils/Misc/IonCloudTest/Coil.jpg
>>
>> Thus, I can inject the ~250kHz signal into the coil riding on top of say
>> 50kVDC :-)
>>
>> I then set up my antenna and scope to measure the resonant signal. The
>> scope was set to read Vrms over many cycles to give a nice stable reading:
>>
>> http://hot-streamer-dot-com/TeslaCoils/Misc/IonCloudTest/Antenna.jpg
>>
>> http://hot-streamer-dot-com/TeslaCoils/Misc/IonCloudTest/Scope.jpg
>>
>> So I could detect if the signal strength dropped (from coil detuning) as
>> the coil was charged from 0 to 50kVDC. The "Q" of the coil setup was about
>> 15.8 (253/16).
>>
>> Here is the measured signal strength of the resonant tuned signal as a
>> function of terminal voltage.
>>
>> Voltage (kVDC) Signal Level (Vrms)
>> 0 2.28
>> 5 2.28
>> 10 2.28
>> 15 2.28
>> 20 2.28
>> 25 2.29
>> 30 2.29
>> 35 2.29
>> 40 2.29
>> 45 2.29
>> 50 Corona Inception
>>
>> The slight change in voltage seemed real but was at the edge of the
>> system's measurement capability and may have been due (probably) to the
>> power supply's switching signal leaking through. At 50kVDC you could hear
>> corona breaking out pretty heavily so I stopped in fear I may pop the TCT.
>>
>> In conclusion, I found no evidence that the coil's DC potential had any
>> affect on the system's resonant frequency
>>
>> Cheers,
>>
>> Terry
>>
>> At 08:39 AM 2/28/2002 +1300, you wrote:
>> >Hello all,
>> > For a long time now, many have suggested that an ion cloud
>> >hanging around the secondary terminal necessitates detuning the
>> >primary downward somewhat to compensate. I have long doubted this
>> >mantra (without proof) but have devised a relatively simple test that
>> >could be performed to establish where the truth lies. My doubt arises
>> >as I think that any detuning of the secondary can be explained (I
>> >think) by capacitance (and resistance) added visible streamer length
>> >alone.
>> > The test does not involve spark production (important).
>> >Instead, one uses the usual setup of a signal generator and aerial
>> >probe to monitor the secondary ringing alone, and then introduce an
>> >ion cloud around the terminal using some other devices (like ozone
>> >generators. UV generators etc. Any significant shift in secondary
>> >frequency should be quite observable.
>> > I think this is an appropriate forum to check this out and add
>> >to the knowledge base. Is anyone equipped to easily do this test?
>> >
>> >Regards,
>> >Malcolm
>> >
>