A measure of capacitance on a capacitance meter might show value similar to the label on the capacitor’s cylindrical body. However, it is not only the capacitance that ensures functionality. Another measurement that needs to be considered is the ESR measurement. ESR is the abbreviation of Electrical Series Resistance. This measure of resistance is specifically during rapid charging and discharging of the capacitor. Given a frequency input, a new good capacitor measures low ESR typically lower than 1 ohm. ESR higher than 1 ohm indicates that the capacitor needs to be replaced so that the circuit employing it can function according to specification.
Department Bio-Medical Engineering, Faculty of Electrical Engineering, Universiti Teknologi Malaysia