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The range of units used to specify capacitor values has expanded to include everything from pico- (pF), nano- (nF) and microfarad (μF) to farad (F). Millifarad and kilofarad are uncommon. The percentage of allowed deviation from the rated value is called tolerance. The actual capacitance value should be within its tolerance limits, or it is ...
For brevity, the notation omits to always specify the unit (ohm or farad) explicitly and instead relies on implicit knowledge raised from the usage of specific letters either only for resistors or for capacitors, [nb 1] the case used (uppercase letters are typically used for resistors, lowercase letters for capacitors), [nb 2] a part's appearance, and the context.
Larger values can be made by multiple stacks of plates and disks. Larger value capacitors usually use a metal foil or metal film layer deposited on the surface of a dielectric film to make the plates, and a dielectric film of impregnated paper or plastic – these are rolled up to save space. To reduce the series resistance and inductance for ...
These values are derived from the mathematical constant e, where % and %. The following formulae use it, assuming a constant voltage applied across the capacitor and resistor in series, to determine the voltage across the capacitor against time:
Although solid tantalum capacitors offered capacitors with lower ESR and leakage current values than the aluminium electrolytic capacitors, a 1980 price shock for tantalum dramatically reduced the applications of tantalum electrolytic capacitors, especially in the entertainment industry.
More sophisticated instruments use other techniques such as inserting the capacitor-under-test into a bridge circuit. By varying the values of the other legs in the bridge (so as to bring the bridge into balance), the value of the unknown capacitor is determined. This method of indirect use of measuring capacitance ensures greater precision.