The VIC with resonant cavity project by Steve..

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I´m using that meter Ronie made us buy... my reading for that cell with very pure water is 1nf round... when water has some 20ppm it goes to 20nf measured..

calculation in my opinion is the only way to be sure our reading is true...so we should try to support our measurements by calculated values and compare

to calculate for concentric cylinders

http://hyperphysics.phy-astr.gsu.edu/hbase/electric/capcyl.html

the its a metric calculator

for the inner radius is (half the diameter) of the rod so i used 0.00635 for the inner
for the outside radius (half the inner diameter of the tube) 0.0089
for length 0.06985

the results were close to what i have here...

around 900pf with water calculated compared to 1nf

and around 11 pf so like i told you around 10pf measured value..

so i think maybe you should check your meter bro...

i think 10% error is ok

or maybe you should try to take everything out and clean all the moisture  before measuring... i don't know..

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Steve, meters will not behave good with water capacitor.
Measuring the cell completly dry and multiply by the dielectric constant is your near option.
You can run a parallel plate capacitor formula for coaxial ones:

- Get the circumference of the outer surface from inner tube (i.e. 0.5" x PI or radius^2 x PI)
- Get the circumference of the inner surface from outer tube (i.e. 0.69" x PI or radius^2 x PI)

- sum both and multiply by the shortest height overlapping (i.e. outer tube - 2,75")
 You  have now the area.

- calculate the gap (i.e. 0.69-0.5 /2 =0.095)


- get the dielectric constant (78.54) and calculate on:
http://www.daycounter.com/Calculators/Plate-Capacitor-Calculator.phtml
 

Try it and confirm what I told you when you measured and multiplied by the water dielectric constant.

But this is not only the  LC series that play all the role.

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a thought that just occurred to me is that maybe the capacitance reading get higher with higher conductivity water or higher ppm is because it may measure the capacitance as a impedance and as the conductive properties appear in parallel it will appear as a lower xc thereto showing higher capacitance...

i think we should stay with the capacitance calculated value... a formula can be build to calculate the deviation on the resonant frequency by the resistive load in parallel with the C but i would not wast my time either... meyer told the deviation in resonant frequency for given ppm.

i´m using the formula Turns= V/bmax/m2/Hz/4 as a rule for designing the chokes to take advantage of the core using square input... both chokes suppose to be the same and to resonate at 5khz with 1 cell it must form 1Henrie... each.. 
 
Brother in my last analysis i discovered a new thing..

i was looking at the vic sync image and realised its the same as what i came up with..

basically i splited the vic in 3 sections

first is simple primary and secondary with center tap

second is the chokes that will receive pulses of one polarity each being each connected to a diode at the extremities of the l2 and where it makes the magic i will talk later on the chokes are than connected together and connected to a center rod of the cell

the third is a coil that will receive mainly unipolar current  from the outside tube of the cell  and is connected to the center tap of the secondary

this form the vic so to clear and glue the idea the secondary is a full wave bridge with center tap but the diodes don't connect to each other they have the chokes connected there between.. this will also double the frequency

the third coil will create a magnetic field as pulses go on as it will receive only dc current pulses... i believe this is the amp inhibiter coil and it kind of make part of the resonance but should be wound on a high saturation material as core...

i  kind of get the feeling that this magnetic field will change the game...

stan somewhere mention the 3 coil design...

i splited all to understand and i think this is what he represented on the drawings...

i used 2 diodes he may not have show the whole picture...

i recognise him all the right to have done this to protect the tech..
 

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Thanks guys.
An easy answer is sadly not easy.

I did some measurements on a new set of Meyer electrode of the same serie i bought.
Inner rod measures between the two end holes a 64mm lenght.
The outside diam is 12.9mm

The outertube measures a inner diam of 17.37mm and has a lenght of 71.2mm
It seems i have a 2mm gap between the 2 electrodes.

source: https://electronicspani.com/cylindrical-capacitor/
Relative Permittivity of the medium air = 1 and for water at 20 degrees celcius is 80
Length of cylinder = 0.0172m
Radius inner cylinder = 0.0064m
Radius outer cyinder inside wall = 0.008685m

Creates a capacity of 13pF with air as dielectric and a 1nF with water as dielectric
All according to this calculator.
My meter shows different measurements: with air, it is between 38pF and 35pF.
This might be the case of the humidity and temperature of the air of my livingroom.........

Yr thoughts?

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source: http://www.k7mem.com/Electronic_Notebook/capacitors/coaxial_cable.html

outcome is:
d = 0-1/2", 1.29 cm, 12.9 mm
D = 0-11/16", 1.737 cm, 17.37 mm
C = 25.12 pF/ft, 82.4 pF/Meter
As my tubes are .0712 meters long, the capacitance should be:
82.4 / 100 * 0.0712 = 5.8pF

HEADACHE!!!!!!!!

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Here confirmation of the first calculator:
https://www.vcalc.com/wiki/TylerJones/Capacitance+of+a+Cylindrical+Capacitor

13pF with air and 1nF with water

This equation can be derived from Gauss's Law and the relation q = CV 1.

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I´m using that meter Ronie made us buy... my reading for that cell with very pure water is 1nf round... when water has some 20ppm it goes to 20nf measured..

calculation in my opinion is the only way to be sure our reading is true...so we should try to support our measurements by calculated values and compare

to calculate for concentric cylinders

http://hyperphysics.phy-astr.gsu.edu/hbase/electric/capcyl.html

the its a metric calculator

for the inner radius is (half the diameter) of the rod so i used 0.00635 for the inner
for the outside radius (half the inner diameter of the tube) 0.0089
for length 0.06985

the results were close to what i have here...

around 900pf with water calculated compared to 1nf

and around 11 pf so like i told you around 10pf measured value..

so i think maybe you should check your meter bro...

i think 10% error is ok

or maybe you should try to take everything out and clean all the moisture  before measuring... i don't know..

Maybe my meter is not good.....
Will run some tests.
TENMA 72-8155

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Ill guess that the 1nF is workable number........
That gives me the need of 14milliHenry if i want to achieve resonance at 42khz

cheers