Measured value for various high voltage terminals

To: tesla-at-pupman-dot-com
Subject: Measured value for various high voltage terminals
From: Tesla List <mod1-at-pupman-dot-com>
Date: Thu, 2 Oct 1997 21:51:20 -0600 (MDT)
Approved: mod1-at-poodle.pupman-dot-com


---------- Forwarded message ----------
Date: Thu, 2 Oct 1997 22:39:23 -0500
From: "DR.RESONANCE" <DR.RESONANCE-at-next-wave-dot-net>
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Measured value for various high voltage terminals

To: Tesla List

One day last month we got ambitious and set a number of various size high
voltage terminals high atop an insulated column and then measured their
capacitance.  Thought these values might be of interest to TC builders in
the group:

 7 inch dia sphere - - - - - - - - -	14 pF

14 inch dia sphere - - - - - - - - 	22 pF

30 inch dia sphere - - - - - - - -	44 pF

40 inch dia sphere - - - - - - - -	60 pF

1 3/4 x 7 inch toroid - - - - - - -	9 pF

8 x 3 toroid - - - - - - - - - - - - - 	11 pF

12 x 3 toroid - - - - - - - - - - - -	16 pF

14 x 4 toroid - - - - - - - - - - - -	25 pF

24 x 6 toroid - - - - - - - - - - - -	38 pF

34 x 8 1/2 toroid - - - - - - - - -	50 pF

48 x 12 toroid - - - - - - - - - - -	67 pF

"Average" electric field capacitance for small oscillator with 6-14 inch
spark is approx 7.5 pF

"Average" electric field capacitance for med oscillator with 14-30 inch
spark is approx 20 pF

"Average" electric field capacitance for large oscillator with 3-9 ft spark
is 35-50 pF (at 5-7 kva)

These values do not include the self "distributed" capacitance of the
secondary inductor and do include the capacitance of the high voltage
terminal.  Terminal values are listed above and self capacitance can easily
be determined by measuring the inductance and resonant freq of the
inductor.  From these two measured values the capacitance can be determined
with simple algebra.  The terminal capacitance and electric field
capacitance can be added to these values by taking a snapshot (best to take
about 2 dozen) of a normal scope with antenna pickup set at a distance from
the coil while it is running and in tune.  The resonant freq is then
measured directly from the scope snapshot by knowing the sweep speed of the
scope setting and a bit of math.  The freq is equal = Fr = 1/t where t is
the period of the oscillation.  When the actual operating freq is found
then the difference in frequencies and the known measured inductance is
used to find the change in the value of capacitance.  Already knowing the
capacitance of your high voltage terminal you can now subtract the
capacitance difference between the two values.  The remaining value is the
capacitance of your electric field above the coil while it is running. 
This value is important because it can be scaled up to assist in the design
of future coils.

DR.RESONANCE-at-next-wave-dot-net