Any electronic element, in addition to its main characteristic (capacity, for example), is described by a number of indicators associated with the physical features of the structure. The ESR of a modern capacitor is its equivalent resistance in series. For the competent use of this element in pulse electronic circuits, it is important to know what it is and how it is taken into account in calculations and in practice.
Real parameters of the capacitor
Before using a typical capacitor (simple or electrolytic) in working circuits, first of all, you should familiarize yourself with a set of its characteristics.
The following typical parameters are used to describe a real capacitor element:
- R is the resistance to the current of the dielectric between the plates.
- C is the capacitance of the capacitor.
- ESR is the parameter we are considering.
- ESI (or ESL) is its reduced inductance (photo below).
In this list, we are only interested in the third element, the need to take into account which arose with the advent of pulse converters. Relatively high frequencies forced the developers to pay attention to the ESR of capacitors, in which losses could no longer be neglected (as was done earlier in low-frequency circuits).
Formula for calculation
The parameter we are considering is determined by the following formula:
Here, the first term is the resistance of the aluminum plate, the second is the same indicator, but in relation to the electrolytic plate. The third term corresponds to the resistance of the dielectric, and the fourth to the same parameter for the working terminals.
Electrolytes and measurement of the desired indicator
Note that in most cases ESR refers specifically to electrolytes, whose characteristics begin to "float" when heated. Excessive heating is the most common cause of unnatural aging of a capacitor and subsequent "swelling".
At the same time, the ESR indicator begins to grow, although its capacity remains within the nominal value. It is not very convenient to take up a calculator and calculate the required value every time you need to determine its value. It is much easier and more convenient to determine it using modern instruments designed specifically for measuring resistance.
Loss measurement
To obtain a result in this way, you will need an LCR meter from a Chinese or some other manufacturer (photo below).
With its help, it is possible to measure not only the capacitance of the controlled element, but also the resistance at a relatively high frequency. After that, the user will only have to compare it with the values admissible for this scheme, given in special tables.