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Re: Measuring Capacitance (fwd)



---------- Forwarded message ----------
Date: Fri, 24 Apr 1998 01:37:11 -0500
From: "Barton B. Anderson" <mopar-at-mn.uswest-dot-net>
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Re: Measuring Capacitance (fwd)

Patrick,
I personally use an LCR meter. Makes it quick and easy. If you don't have
one or access to one, you might just take the caps over to a local
electronic fix-it shop and have them measure it for you. It's only a couple
seconds of their time.
|_Bart_|

Tesla List wrote:

> ---------- Forwarded message ----------
> Date: Fri, 24 Apr 1998 00:23:53 +0000
> From: "Patrick J. Gustafson" <gustafpj-at-uwec.edu>
> To: Tesla List <tesla-at-pupman-dot-com>
> Subject: Measuring Capacitance
>
> Hello All:
>
>     What is the preferred method of physically finding the actual
> capacitance of a capacitor?  Does anybody still use impedance bridges?
> I use an impedance bridge that I use in conjunction with a frequency
> generator, then I can do both capacitance and inductance measurements
> (comes in real handy for finding the inductance of chokes with different
> cores).  However, here is my situation:  I made a couple of rolled
> capacitors using LDPE as the dielectric.  Using the k-value of 2.2 and
> the physical dimensions of the capacitor, I have a calculated
> capacitance to be approximately .00644 micro-farads for each.
>
>     Now when I use the impedance bridge on the capacitance setting, I
> run an audible frequency through the capacitor and search for nodal
> points in the amplitude of the sound wave (indicating matching
> impedances for the plates), I then get a capacitance value of .021
> micro-farads!  This was certainly an unexpected surprise.  A gain of
> almost .015 micro-farads!
>
>     I have not directly measured the actual k-value of the LDPE, but I
> suspect that it does not deviate far from the 2.2 mark.  If in fact the
> bridge is working properly, I believe that the real culprit of the added
> capacitance is in the oil that I used (Caltron 60/30).  I received 10
> gal. from the local power company for free. They use the same oil in all
> of their high voltage pole transformers.  I now of course would like the
> determine the value of this oil, but I am hesitant to use the bridge.
> So, back to my original question, what does everyone else use to measure
> capacitance?
>
> Patrick Gustafson, Capacitance to Spare in Eau Claire.