The capacitance is not always indicated directly on the capacitor in units derived from the farad. Manufacturers often use abbreviations and codes to reduce the size of markings. On electrical diagrams, special abbreviations are also found in the designation of capacity.
Instructions
Step 1
If you have an electrical schematic diagram, made according to the old standard, then the designations of the capacitance in which a comma is present, regardless of whether the fractional part is equal to zero, are always expressed in microfarads. For example: 0, 015;
50, 0. If there is no comma in the designation, then the capacitance of the capacitor is expressed in picofarads, for example: 5100;
200.
Step 2
In modern circuits, the capacitance of a capacitor, expressed in microfarads, is always denoted by the abbreviation "mk" (not "mkF"). The comma may or may not be present. For example: 200 microns;
0.01 μ. The designations of the capacitance, expressed in picofarads, did not undergo changes during the transition to the new standard.
Step 3
A slightly different way of designating capacitance is used when marking the cases of the capacitors themselves. The designation "pF" or the complete absence of the name of the unit of measurement indicates that the capacitance is expressed in picofarads. Microfarads are designated using the abbreviation "uF". Nanofarads are denoted by the Russian letter "n" or the Latin letter n. If part of the numbers is before this letter, and the other part is after, then the letter itself is equivalent to a comma. For example, read the designation "4n7" as "4, 7 nanofarads".
Step 4
On miniature capacitors (including the SMD form factor), the capacity is designated using special codes consisting of numbers and letters. When decoding them, be guided by the document located at the link given at the end of the article.
Step 5
Remember that capacitance is not the only characteristic of a capacitor. When using it in pulse circuits, such a parameter as the equivalent series resistance is important, in high-frequency circuits - parasitic inductance. Often, neither one nor the other is marked on the device case, and these parameters have to be measured. It is also important to know the polarity of switching on the capacitor, if it is electrolytic, and its nominal voltage. On the imported capacitor, next to the negative terminal, there is a long strip of hyphens, and on the domestic one, next to the positive terminal, there is a plus sign. A special marking method is used on capacitors of the K50-16 type: both polarity signs (plus and minus) are stamped on the plastic bottom of the element.
