Basic knowledge of capacitors and detection methods
A basic knowledge: a capacitor is an energy storage element used in the circuit for tuning, filtering, coupling, bypassing, energy conversion and delay. Capacitors are often called capacitors. According to its structure can be divided into fixed capacitors, semi-variable capacitors, variable capacitors three.


1. The structure and characteristics of commonly used capacitors
Commonly used capacitors can be divided into electrolytic capacitors according to their dielectric materials, mica capacitors, ceramic capacitors, glass glaze capacitors and so on.


Aluminum electrolytic capacitors
    It is made of aluminum cylinder to do the negative, which is equipped with liquid electrolyte, insert a curved aluminum belt made of positive electrode. Also need to go through the DC voltage treatment, so that the formation of an oxide film on the positive film to do the media. It is characterized by large capacity, but leakage large, large error, poor stability, often used for AC bypass and filter, when the request is not high when used for signal coupling. Electrolytic capacitors are positive and negative points, the use can not be reversed. There are positive and negative polarity, the use of time, positive and negative do not reverse.

The paper dielectric is made of two pieces of metal foil, made of very thin capacitor paper, rolled into a cylindrical or flat cylindrical core, and then sealed in a metal shell or insulating material (such as paint, ceramic, glass glaze, etc.) production. It is characterized by a smaller size, capacity can be done bigger. But there are inherent inductors and losses are relatively large, suitable for low frequency.


Metallized paper dielectric structure and paper dielectric capacity is basically the same. It is in the capacitor paper coated with a layer of metal film instead of metal foil, small size, large capacity, generally used in low-frequency circuit.


1. It is the ability to enhance its pressure by immersing the paper capacitor in a specially treated oil. It is characterized by large capacity, high pressure, but the larger.


Glass glaze capacitors to glass glaze for the media, with the advantages of ceramic capacitors, and smaller, high temperature.
Ceramic capacitors are made of ceramic, and the silver layer is sprayed on both sides of the ceramic substrate, and then the silver film is made into a silver plate. It is characterized by small size, good heat resistance, low loss, high insulation resistance, but the capacity is small, suitable for high-frequency circuit.
Ferroelectric ceramic capacitor capacity is large, but the loss and temperature coefficient is large, suitable for low frequency circuit.


Film capacitors
The structure is the same as the paper dielectric, the medium is polyester or polystyrene. Polyester film capacitors, high dielectric constant, small size, large capacity, good stability, suitable for bypass capacitors.
Polystyrene film capacitors, dielectric loss is small, high insulation resistance, but the temperature coefficient, can be used for high-frequency circuit.