Re: Capacitance Measurement Question

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

Original poster: "Brian Foley by way of Terry Fritz <twftesla-at-uswest-dot-net>" <ka1bbg1-at-mcttelecom-dot-com>

Hi all, many capacitors do change with temperature. some are rated others
not. I also have had capacitors change value as they warm up causing
intermitted electronic operation.(drift tuned circuits will get out of tune)
cul brian
----- Original Message -----
From: Tesla list <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Wednesday, December 27, 2000 1:38 PM
Subject: Capacitance Measurement Question


> Original poster: "by way of Terry Fritz <twftesla-at-uswest-dot-net>"
<Tesla729-at-cs-dot-com>
>
> Hi all,
>
> Hoping everyone had a Merry Christmas :-) One of the items of
> my Christmas wish list that made it under my tree was a new
> DMM that could measure capacitance. Yes, up till now, I've done
> all of my coiling measurements without the benefit of a means for
> measuring my caps. The DMM is a Velleman made in China and
> was pretty cheap, but it seems to work well and I'm sure it will suf-
> fice for my needs :-)
>
> Now to my question. I noticed that when measuring the capacitance
> of my various capacitors that there will often be a variability in the
> measurement readings that I get on the same capacitor from one
> reading to the next. It seems that it can vary by around ~ 10% or so.
> I'm figuring that the difference in ambient temperature can cause a
> drift in the capacitance. It is ~ 70* F in the house and around 30*F
> outside (yesterday). One of the coldest Decembers on record in my
> area has made experimenting in an unclimate-controlled shop a lit-
> tle uncomfortable (I do have a small kerosene heater). I noticed on the
> manual with the DMM stated that the calibration is guaranteed for a
> year, when the ambient temp is kept in the 18*C to 28*C range. So
> maybe cold temps affect the accuracy of the DMM itself?
>
> I thought I would throw this question out to the list as there couldn't
> be a more authoritative think-tank out there regarding this matter :-)
>
> David Rieben
>
>
>
>