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Re: measurement of capacitance



At 10:35 AM 3/22/99 -0500, you wrote:
How does a multimeter measure capacitance?

just a quick semi-educated guess -

the meter provides a small CONSTANT current and measures the TIME required
for the voltage to rise by a given amount. (Constant current sources are
easy to come up with for these limited voltage ranges)
Chuck,
Your close it dosen't need to be that complex. Most of these just
measure the time necessary to charge the capacitor to a preset voltage
through a known resistor. C = deta t/ R. If the source voltage is constant,
you can ajust R to give various ranges in C.Leacky capacitors (ones with a
low internal resistance) limit the accuracy of this technique. The old
fashion bridges could cancle out the effects of this internal resistance.
I hope this helps
Gary
Gary Karshner

St. Mary's University
San Antonio, Texas
KARSHNER@STMARYTX.EDU