电桥的概念：用比较法测量各种量（如电阻、电容、电感等）的仪器。最简单的是由四个支路组成的电路。各支路称为电桥的“臂”。如图电路中有一电阻为未知（R2），一对角线中接入直流电源U，另一对角线接入检流计G。可以通过调节各已知电阻的值使G中无电流通过，则电桥平衡，未知电阻R2=R1·R4/R3。测量结果的意义：
The concept of a bridge: an instrument that uses a comparative method to measure a variety of quantities (such as resistance, capacitance, inductance, etc.). The simplest is a circuit consisting of four branches. Each branch is called the "arm" of the bridge. Figure in a circuit for the unknown resistor (R2), access U DC power supply a diagonal line, a diagonal access G galvanometer. The balance of the bridge and the unknown resistance R2=R1 R4/R3 can be achieved by adjusting the values of the known resistors in the G. The significance of the measurement results:
C：被测电容器的电容分量
C: the capacitance component of the measured capacitor
R：被测电容器的阻性分量
R: the resistive component of the measured capacitor
Φ：被测电容器的电容量与阻性分量之间的夹角
The angle between the capacitance and the resistive component of the measured capacitor
U：加在被测电容器的交流电压
U: AC voltage added to the measured capacitor
I：通过被测电容器的交流电流
I: AC current through the measured capacitor
P：被测电容器的功率损耗
P: power loss of the measured capacitor
Q：对应电压等级下电容的无功功率
Q: reactive power of capacitance at corresponding voltage level
F：测量电压的频率
F: measuring the frequency of the voltage