Capacitors, often referred to simply as capacitors for their ability to hold charge, are denoted by the letter C. Definition 1: A capacitor, as its name implies, is 'a container for electricity', a device that holds an electric charge. English name: capacitor. capacitor is one of the electronic components used in a large number of electronic devices, widely used in circuit isolation through the cross, coupling, bypass, filtering, tuning circuit, energy conversion, control, etc.. Definition 2: Capacitor, any two conductors (including wires) that are insulated from each other and are close together constitute a capacitor.

General formula C=Q / U parallel plate capacitor special formula: the electric field strength between the plates E=U/d, capacitor capacitance determinant C=εS/4πkd

With the rapid changes in electronic information technology, digital electronic products are updated more and more quickly to flat-panel TVs (LCD and PDP), notebook computers, digital cameras and other products based on the production and sales of consumer electronics products continue to grow, driving the growth of the capacitor industry. And led to the development of related materials, equipment industry, China has become the world's leading producer of capacitors.

1, the detection of fixed capacitors

A Detection of small capacitors below 10pF
Because the capacity of fixed capacitors below 10PF is too small, measurement with a multimeter can only qualitatively check whether there is leakage, internal short circuit or breakdown phenomenon. Measurement, you can choose the multimeter R × 10k block, with two pens were connected to any two pins of the capacitor, the resistance value should be infinity. If the measured resistance (pointer swing to the right) is zero, then the capacitor leakage damage or internal breakdown.

B test 10PF ~ 0 01μF fixed capacitor whether there is charging phenomenon, and then determine whether it is good or bad.
Multimeter selection R × 1k block. Two transistor value are more than 100, and the penetration current should be small. Can choose 3DG6 and other models of silicon transistors to form a composite tube. The red and black pens of the multimeter are connected to the emitter e and collector c of the composite tube. Due to the amplifying effect of the composite transistor, the measured capacitance of the charge and discharge process to be amplified, so that the multimeter pointer swing amplitude increased, thus facilitating observation. It should be noted that: in the test * work, especially in the measurement of smaller capacitance, to repeatedly switch the measured capacitance pin contact A, B two points, in order to clearly see the multimeter pointer swing.

C for more than 0 01μF fixed capacitors, the multimeter can be used to directly test the capacitor with or without charging process as well as internal short circuit or leakage, and according to the magnitude of the pointer to the right of the magnitude of the swing estimate the capacity of the capacitor.

2,Electrolytic capacitor test
A Because the capacity of electrolytic capacitors is much larger than that of general fixed capacitors, therefore, when measuring, the appropriate range should be selected for different capacities. According to experience, in general, 1 ~ 47μF capacitance, available R × 1k block measurement, greater than 47μF capacitance can be R × 100 block measurement.

3,Variable capacitor detection

C will be placed in the multimeter R × 10k block, one hand will be two pens were connected to the variable capacitor of the moving piece and fixed piece of the lead, the other hand will be slowly rotating the rotary axis a few times back and forth, the multimeter pointer should be in the position of infinity immobility. In the process of rotating the rotary axis, if the pointer sometimes points to zero, indicating that there is a short-circuit point between the moving piece and the fixed piece; if encountered at a certain angle, the multimeter reading is not infinity, but a certain resistance, indicating that there is a leakage of variable capacitors between the moving piece and the fixed piece.