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Re: dielectric constants
From: Thomas McGahee[SMTP:tom_mcgahee-at-sigmais-dot-com]
Sent: Tuesday, November 04, 1997 7:07 AM
To: Tesla List
Subject: Re: dielectric constants
> From: Teslaman-at-aol-dot-com[SMTP:Teslaman-at-aol-dot-com]
> Sent: Monday, November 03, 1997 4:30 PM
> To: tesla-at-pupman-dot-com
> Subject: dielectric constants
>
> All..
>
> After hearing of different oils and dielectric constants for capacitor
> building, I ran a simple experiment. Using a variable capacitor from an old
> tube type radio and measuring its capacitance with air as the dilectric, and
> then immersing in different oils I have come up with a list of dielectric
> constants.
>
> The capacitor had a full mesh reading of .96 nF. The capacitor was cleaned
> in solvent & air blowed dry between each oil immersion. For the 90w oil
> test, the oil was heated to 100 deg.F. to saturate the capacitor plates
> better.
>
>
> capacitance
> diel. constant
>
> begining capacitance in air. .96 nF
> 1
>
> In pharmaceutical mineral
> oil (or baby oil) 2.08 nF
> 2.17
>
> In canlola cooking oil 3.28 nF
> 3.42
>
> in 90w mineral gear oil
> at 100 deg F 18 nF
> 18.75
>
> in 30w motor oil 55 nF
> 57.3
>
> As can be seen there is a wide range, can't figure the high motor oil
> reading though, possible additives causing high readings? Any comments or
> suggestions?
> I'll perform break down voltages for each oil on another day. Of coarse a
> high dielectric constant does not necessarily make it a good choice for
> capacitor construction. The flash points may make some dangerous to use if a
> spark occured in a sealed capacitor with any air in the enclosure. Also the
> thicker the oil the more easily the high voltage electric field will force it
> away from the foil edges of a capacitor as noted in other experiments of
> past.
>
> Kevin E.
>
>
Kevin,
If there are additives in the oil, then the high readings may in fact be due to
conductance rather than capacitance. Some capacitance meters measure the ac
current flow, and any conductance is displayed as if it were capacitance. You
can check this out by paralleling the capacitor with a high value resistor
(100s of K to Megohms). If the capacitance read goes UP appreciably, then it is
affected by conductance. Use a digital OHM meter on its highest range and see
if the oil has any measureable conductance. If so, you have identified the
source of error.
Fr. Tom McGahee