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Capacitor Markings

The vast majority of capacitors employ written markings which indicate their values, working voltages, and tolerance. The most usual method of marking resin dipped polyester, and other types of capacitor involves quoting the value (in μF, nF or pF), the tolerance (often either 10% or 20%), and the working voltage. Several manufacturers use two separate lines for their capacitor markings and these have the following meanings: First line: capacitance (in pF or μF) and tolerance (J=5%, K=10%, M=20%). Second line: rated d.c. voltage and code for the dielectric material.

A three-digit code is often used to mark monolithic ceramic capacitors. The first two digits correspond to the first two digits of the value whilst the third digit is a multiplier which gives the number of zeros to be added to give the value in pF.

Finally, it is essential to note that electrolytic capacitors (often those with larger values) require a d.c. polarizing current in order to operate correctly. Furthermore this voltage must be applied with the correct polarity. The terminals of electrolytic capacitors are therefore marked with symbols (often + and - ) to indicate the correct polarity - failure to obseve these markings when connecting a capacitor into a circuit can be catastrophic!

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Page last modified on July 21, 2011, at 03:51 PM