Capacitor numeric marking codes
Capacitor marking or code systems are often used to indicate the value and other parameters on a capacitor. Large capacitors are able to have their values marked on the case, but on smaller ones there is insufficient space to give the data and capacitor code systems are required. Some use a colour code, but increasingly capacitors used a figure code is used on the smaller capacitors.
On a large electrolytic capacitor there is sufficient space to mark the value, the tolerance, working voltage, and often other data such as the ripple voltage. Smaller capacitors may only have room for a few figures printed as a code for the value.
On one scheme there may just be two figures. These refer to the capacitance in picofarads, i.e. 10 is 10 pF.
Another scheme uses three or four characters. It bears many similarities to the colour code system adopted for resistors, but without the colour part of the coding scheme. The first two figures refer to the significant figures, whereas the third one acts as a multiplier. The value of the capacitor being denoted in picofarads.
By Ian Poole
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