What is ESR and how can it be tested?
ESR (Equivalent Series Resistance) is an important parameter of any capacitor. It represents the effective resistance resulting from the combination of wiring, internal connections, plates, and electrolyte (in an electrolytic capacitor). The ESR affects the performance of tuned circuits (high ESR reduces the Q factor) and may result in totally incorrect or unstable operation of devices like switchmode power supplies and deflection circuits in TVs and monitors. As would be expected, electrolytic capacitors tend to have a high ESR compared to other types – even when new. However, due to the electrochemical nature of an electrolytic capacitor, the ESR may indeed change – and not for the better – with time. When troubleshooting electronic equipment, electrolytic capacitors, in particular, may degrade resulting in a significant and unacceptable increase in ESR without a similar reduction in uF capacity when measured on a typical DMM’s capacitance scale or even a cheap LCR meter. There comme
