Main parameters of capacitors.
1. When the temperature coefficient changes, the capacity of the temperature capacitor will change slightly, and this characteristic is usually indicated by the temperature coefficient. The temperature coefficient refers to the relative change of capacitor capacity when the temperature changes 1 degree Celsius in a certain temperature range.

 
2. The nominal capacity and the allowable error nominal capacity are marked on the capacitor. There is a certain error between the actual capacity and the nominal capacity of the capacitor, and the maximum allowable error between the nominal capacity and the actual capacity of the capacitor is called the allowable error of the capacitor. The error between the nominal capacity and the actual capacity of the capacitor reflects the accuracy of the capacitor.

3. The characteristic that electrical parameters such as capacitance change with the change of the operating frequency of a circuit. If the dielectric material of the capacitor is different, the maximum operating frequency of the capacitor is also different. For example, high-frequency ceramic capacitors or mica capacitors with small capacity need to be used in high-frequency circuits, while capacitors with larger capacity (such as electrolytic capacitors) can only operate normally in low-frequency circuits.

4. The energy consumed by a dielectric loss capacitor in an electric field is generally expressed by the ratio of the loss power to the reactive power of the capacitor, that is, the tangent of the loss angle. The larger the loss angle, the greater the loss of the capacitor (not suitable for working at high frequency).

5. The ratio of the voltage added to both ends of the capacitor to the leakage current passing through the capacitor is equal to the insulation resistance of the insulation resistance capacitor. The insulation resistance is related to the dielectric material, area, lead material and length, manufacturing process, temperature and humidity of the capacitor. For capacitors of the same medium, the larger the capacitance is, the smaller the insulation resistance is. The size and change of the insulation resistance of capacitors will affect the working function of electronic equipment, so the larger the insulation resistance of the usual electronic equipment, the better.

6. Additional operating voltage refers to the capacitor in a certain temperature range, can be connected to the highest point voltage of reliable operation, which is divided into additional DC operating voltage and additional communication operating voltage. The extra operating voltage is related to the medium and ambient temperature used in the capacitor. With different ambient temperature, the maximum operating voltage that the capacitor can accept is also different. When selecting a capacitor, according to the magnitude of its operating voltage, select a capacitor whose additional operating voltage is higher than the actual operating voltage to ensure that the capacitor will not be broken down. The commonly used fixed capacitor operating voltages are 6.3V, 10V, 16V, 25V and so on. The withstand voltage value is usually directly marked on the capacitor, but the withstand voltage of some electrolytic capacitors is color-coded, and the orientation is close to the root of the positive lead line.

7. The medium of the leakage current capacitor is not absolutely insulated, there will always be some leakage. Usually, the leakage current of electrolytic capacitors is relatively large, while the leakage current of other capacitors is very small. When the leakage current is large, the capacitor will heat up, and when the heat is serious, the capacitor will be damaged.

电容器的主要参数

1. 温度系数 改变温度电容器容量会发生细微改变，这种特性通常用温度系数来表明。温度系数是指在一定温度范围内，温度每改变1摄氏度时电容器容量的相对改变值。

2. 标称容量与答应差错 标称容量被标志在电容器上。电容器的实际容量与标称容量存在必定的差错，电容器的标称容量与实际容量的答应大差错，称作电容器的答应差错。电容器的标称容量与实际容量的差错反映了电容器的精度。

3. 频率特性 电容量等电参数跟着电路作业频率的改变而改变的特性。电容器的介质材料不一样，其作业频率相应的也不一样。例如，高频电路中需运用容量较小的高频瓷介电容器或云母电容器等，而容量较大的电容器（如电解电容器）只能在低频电路中正常作业。

4. 介质损耗 电容器在电场中消耗的能量，一般用损耗功率和电容器的无功功率之比，即损耗角的正切值来表示。损耗角越大，电容器的损耗越大（不适于在高频情况下作业）。

5. 加在电容器两端的电压与经过电容器的漏电流的比值等于绝缘电阻电容器的绝缘电阻值。绝缘电阻与电容器的介质材料、面积、引线的材料和长短、制作工艺、温度和湿度等要素有关。同一种介质的电容器，电容量越大，绝缘电阻越小。电容器绝缘电阻的大小和变化会影响电子设备的作业功能，所以通常的电子设备，选用的绝缘电阻越大越好。

6. 额外作业电压是指电容器在一定的温度范围内，可以接连牢靠作业的点压，又分为额外直流作业电压和额外沟通作业电压。额外作业电压的大小与电容器所用介质和环境温度有关。环境温度不同，电容器能接受的作业电压也不一样。选用电容器时，要根据其作业电压的大小，选择额外作业电压大于实际作业电压的电容器，以确保电容器不被击穿。常用的固定电容作业电压有6.3V、10V、16V、25V等。耐压值通常直接标志在电容器上，但有些电解电容的耐压采用色标法的，方位接近正极引出线的根部。

7. 漏电流电容器的介质并不是绝缘的，总会有些漏电。通常电解电容器的漏电流比较大，其他电容器的漏电流很小。当漏电流较大时，电容器会发热，发热严重时，电容器会损坏。