In this paper, I present details of building a capacitance meter for measuring electric capacitance of small metalic objects near to each other. An oscillator employing a single bipolar transistor produces a signal whose period in microsseconds can be measured with a conventional osciloscope and a simple equation allows to derive the capacitance in picofarads. An analysis of the instrumental transfer function shows a suitable experimental accuracy for measurements between 2 and 500 pF. The problem of capacitance measurement for a conductive sphere and a plane is analyzed showing a good agreement between theoretical results and the measurements. Other possibilities for approaching other experimental situations in an electromagnetics teaching lab with students and a discussion of resultas are also presented.
method; experimentation; low capacitances
