惠斯通电桥（又称单臂电桥）是一种可以精确测量电阻的仪器。图3－13所示是一个通用的惠斯通电桥。电阻R1，R2，R3，R4叫做电桥的四个臂，G为检流计，用以检查它所在的支路有无电流。当G无电流通过时，称电桥达到平衡。平衡时，四个臂的阻值满足一个简单的关系，利用这一关系就可测量电阻。-Wheatstone bridge (also known as Wheatstone bridge) is an instrument that can accurately measure resistance. Figure 3-13 is a common Wheatstone bridge. Resistors R1, R2, R3, R4 called the four-arm bridge, G for the galvanometer, to check whether it is in the branch current. When no current passes through G, the said bridge balance. Balance, the four arm resistance to a simple relationship between the resistance can be measured by this relationship.