The introduction of capacitor’s characteristics and test methods
Published time: 2018-07-09
What is a capacitor?A capacitor is a passive two-terminal electrical component that stores potential energy in an electric field. capacitor, also known as "capacitance", refers to the amount of charge stored at a given potential difference, denoted as C, and the international unit is Farad (F). Generally, the electric charge moves in the electric field. When there is a medium between the conductors, the electric charge is hindered and the electric charge accumulates on the conductor, causing the accumulated storage of the electric charge. The stored electric charge amount is called a capacitance.Capacitance refers to the ability to accommodate an electric field. Any electrostatic field is composed of many capacitors. There are capacitors in the electrostatic field. Capacitors are described by electrostatic fields. It is generally believed that the isolated conductor forms a capacitance with the infinity, and the conductor ground is equivalent to being connected to infinity and connected to the earth as a whole.
Capacitance is the physical quantity that represents the charge capacity of a capacitor. It is a static charge storage medium. It may be a permanent charge. This is its characteristic. It is widely used. It is an indispensable electronic component in the field of electronics and power. It mainly be used in power supply filtering, signal filtering, signal coupling, resonance, filtering, compensation, charge and discharge, energy storage, DC blocking and other circuits.
How does the capacitor work?
Capacitors are one of the most widely used electronic components in electronic devices. Their working principle is to store electrical energy by storing charge on the electrodes, usually in combination with an inductor to form an LC oscillating circuit. The working principle of the capacitor is that the electric charge will move under the electric field. When there is a medium between the conductors, the electric charge is hindered to cause the electric charge to accumulate on the conductor, resulting in the accumulation of electric charge.
The life of a film capacitor is related to the ambient temperature:Each capacitor's label is marked with its temperature category, for example: "-40/A", which means that the capacitor can be put into the grid at a low ambient temperature of -40 °C. The high ambient temperature for continuous operation of this capacitor is: Ih average high temperature is 40 ° C, 24 h average high temperature is 30 ° C, annual average high temperature is 20 ° C. This is because at a low temperature, the viscosity of the impregnating agent inside the capacitor increases, the internal voltage decreases, and the capacitor's power resistance decreases.
Jotrin Electronics believes that putting it into operation at a temperature lower than its allowable low temperature is likely to cause partial discharge inside the capacitor, thereby accelerating its electrical aging and reducing the actual life of the capacitor. On the other hand, if the capacitor is operated for a long period of time above its high allowable temperature, it will accelerate the thermal aging of the capacitor. Therefore, on the one hand, it is necessary to select a capacitor whose temperature category is compatible with the actual operating environment temperature. On the other hand, in the installation and use of the capacitor, special attention should be paid to the ventilation, heat dissipation and radiation problems of the capacitor under actual use conditions, so that the capacitor is The heat generated during operation can be dissipated in time, and every effort is made to reduce the temperature of the medium inside the capacitor under high temperature conditions, so as to extend the actual service life of the capacitor.
How does Jotrin Electronics to test capacitors:1.test parameters and test conditions
Jotrin Electronics limited generally measures the capacitance values of ceramic capacitors C and Q, and determines whether the parameters of the capacitor are within the specification range. Whether there are defects, but as the market demand diversifies, the types of capacitors are numerous, and the test conditions are not completely uniform. For specific model measurements, the corresponding specifications are required.2. test equipment and fixturesWe generally use the LCR meter, the automatic balance bridge method to measure the capacitance and Q value. The tools include: LCR bridge (Tonghui H283X), tweezers, etc.3. test process
3.1Preheating the tested product
Due to the characteristics of ceramic materials, especially high-capacity materials are selected for high-capacity materials. After a long time, the internal lattice structure changes, the capacitance value will decrease. At this time, the measurement will be biased, so it is necessary to preheat. It is generally carried out at 140 to 150 ° C for 1 hour of heat treatment and then placed for 24 +/- 2 hours.
Start the device power supply and warm it up for half an hour to make the device work stably. Calibration is very important for accurate measurements. Firstly, keep the distance between the two ends of the fixture probe consistent with the length of the device under test, and perform open circuit calibration; then make the two ends of the fixture contact for short-circuit calibration.
If a fixture with a certain length of wire such as 16334A is selected, the CABLE compensation value, such as 1 meter, should be set to reduce the influence of the parasitic parameters brought by the fixture.
3.4 measurement condition setting
Set the appropriate AC voltage and frequency according to the specifications. For capacitors with a capacitance greater than 1uF, turn on the ALC automatic level control function to keep the voltage across the device under test constant during the actual measurement. Otherwise, the measured capacitance is likely to be low.
3.5 parameter display settings and test result records
There are two circuit modes that display measurement results, one is Cp parallel mode and the other is Cs series mode. In general, the small capacitance value is measured by the Cp mode, and the large capacitance value is measured by the Cs mode. But for high Q capacitors, there is little difference between the two. Record the bridge display capacitance results.
With the rapid development of electronic information technology, the speed of digital electronic products is changing faster and faster. The production and sales of consumer electronic products, mainly flat-panel TVs, notebook computers and digital cameras, continue to grow, driving the growth of the capacitor industry. However, the test of the capacitor is related to many factors. The Jotrin Electronics limited test is strictly in accordance with the parameters of the product specification to provide customers with high quality capacitors.
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