Capacitors Blog

Suntan Technology Company Limited
---All Kinds of Capacitors

Dielectric absorption in a capacitor is difficult to characterize accurately because of the very wide range of the time constants involved and because of the high level of performance required in the measuring equipment. To get a good characterization, the capacitor response must be measured for a range of frequencies at least three decades higher and lower than 1/τ0. Frequency domain measurements must be made with vector impedance analyzers that can accurately resolve a small resistive component in a largely reactive impedance (they must be able to accurately measure large values of Q). In the frequency domain the resistive portion of the impedance gives the most information about dielectric absorption. In the time domain, which is usually used for measurement longer than 100 ms, an ammeter is needed with very low bias current and the ability to resolve very low currents. If these instruments are available, then an accurate and complete model can be made, but such a model is often not required. To completely model dielectric absorption would require, in most cases, a range of accuracy that spans ten decades of frequency or more. Generally, however, the application does not warrant such a model and one can get by with a model that is faithful to the behavior of the physical component over a much smaller range of frequencies.