Re: Variation of secondary Q

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

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

Hi Malcolm and All,

I set my big coil up indoors using the techinque below.   I am seeing about
+- 0.5% variation in Q.  That is really low so I am now checking the
stability of the tests equipment to be sure the variation is not there.  So
far, the variation in Q is very small and within the long term drift of the
test equipment.  Probably won't be able to do any outdoor testing till next
week.

Cheers,

	Terry


>Hi Malcolm,
>
>I have not heard back from Paul on this yet but here are some other ideas.
>
>I could directly connect my 2.5pF 10Meg ohm probe (Tek5100) directly to the 
>top of the coil for a read out like this:
>
>http://hot-streamer-dot-com/temp/PaulsQexp-3.gif
>
>The scope could then save a data file like this:
>
>http://hot-streamer-dot-com/temp/TEK00000.CSV
>
>The resonant frequency drops from 84.42 kHz to 82.15kHz so the probe loading 
>is very low (Those are darn good probes!!  Like Pearson stuff, they too are 
>made out of pure money :-))).  I imagine one could back calculate the small 
>probe loading right out.
>
>However, assuming  Vtop = Q x Vin  we can just input 1 volts RMS and read 
>out the top voltage for a direct Q reading along with time and frequency and 
>just have all our data there without needing to do anything but push the 
>save button ;-))  (may have to check for frequency variation)
>
>http://hot-streamer-dot-com/temp/PaulsQexp-4.gif
>
>That almost seems too easy :o)
>
>If this is OK with Paul, it would be very easy to do.  The scope can filter 
>it down and over sample like 512 times to get very high accuracy.  But that 
>is probably over kill.  I am not sure this would be 100% OK with Paul's 
>paper and all, but it should be close enough I would think.
>
>I wonder if the Q variation is not so much the coil changing but the 
>surroundings changing with weather?  The coil is far more stable for 
>temperature and humidity than the ground, walls, ceiling, etc.  Just a 
>thought there.
>
>Cheers,
>
>	Terry
>
>
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