Outer Coating Flame Retarding Epoxy Resin Film Capacitor Epoxy Resin

Outer Coating Flame Retarding Epoxy Resin Film Capacitor Epoxy Resin

Detect with resistance gear

Practice has proved that the charging process of the capacitor can also be observed by using a digital multimeter, which is actually a discrete digital quantity to reflect the change of the charging voltage. Assuming that the measurement rate of the digital multimeter is n times per second, while observing the charging process of the capacitor, n independent and sequentially increasing readings can be seen every second. According to this display feature of the digital multimeter, the quality of the capacitor can be detected and the size of the capacitance can be estimated. Introduced below is the method of detecting capacitors by using the resistance gear of a digital multimeter, which is very useful for instruments without capacitance gears. This method is suitable for measuring large-capacity capacitors ranging from 0.1 μF to several thousand microfarads.

Electric double layer capacitance

It is produced by the confrontation of charges at the electrode/solution interface through the orientation of electrons or ions. For an electrode/solution system, an electric double layer is formed at the interface of the electronically conducting electrode and the ionically conducting electrolyte solution. When an electric field is applied to the two electrodes, the anions and cations in the solution migrate to the positive and negative electrodes respectively, forming an electric double layer on the surface of the electrodes; after the electric field is removed, the positive and negative charges on the electrodes are in phase with the oppositely charged ions in the solution. The attraction makes the electric double layer stable, and a relatively stable potential difference is generated between the positive and negative electrodes. At this time, for a certain electrode, an opposite ion charge equivalent to the charge on the electrode will be generated within a certain distance (dispersion layer) to keep it electrically neutral; when the two electrodes are connected to the external circuit, the The charge migrates to generate a current in the external circuit, and the ions in the solution migrate into the solution to be electrically neutral, which is the charging and discharging principle of the electric double layer capacitor.

filter

Theoretically (that is, assuming that the capacitor is a pure capacitor), the larger the capacitor, the smaller the impedance and the higher the passing frequency. But in fact, most of the capacitors exceeding 1μF are electrolytic capacitors, which have a large inductance component, so the impedance will increase when the frequency is high. Sometimes you will see an electrolytic capacitor with a large capacitance connected in parallel with a small capacitor. At this time, the large capacitor filters low frequencies, and the small capacitor filters high frequencies. The function of the capacitor is to pass the alternating current and block the direct current, and pass the high frequency and block the low frequency. The larger the capacitance, the easier it is for high frequencies to pass. Specifically used in filtering, the large capacitor (1000μF) filters the low frequency, and the small capacitor (20pF) filters the high frequency. Some netizens have vividly compared the filter capacitor to a "pond". Since the voltage across the capacitor will not change abruptly, it can be seen that the higher the signal frequency, the greater the attenuation. It can be vividly said that the capacitor is like a pond, and the water volume will not change due to the addition or evaporation of a few drops of water. It converts changes in voltage into changes in current, and the higher the frequency, the greater the peak current, which buffers the voltage. Filtering is the process of charging and discharging.