The first method is to take more accurate Ln as the standard measurement. If the arm resistance of the bridge is more accurate, then Lx=Ln according to the meaning of the question.

In the second method, it should be clear in the title that L0 is also replaced by Ln, and then the bridge arms are exchanged. When R 1R2 is inaccurate, this method is more accurate than the first method. If R 1R2 is the standard resistance, it has little effect on the AC bridge. Generally speaking, it is more accurate than the first one because it was measured once.

The third method, the measurement result is that the value of Ln is equal to Lo, so how can it be equal to Lx?

In fact, measuring inductance with AC bridge is not the best. Because inductance is a standard, its accuracy is difficult to guarantee, and it is greatly influenced by environment and electromagnetism. Moreover, if the q difference between the standard inductance and the measured inductance is very large, it is not easy to balance.

Therefore, when measuring the inductance in AC bridge, the standard capacitance is generally used as the standard element, and its accuracy is easy to ensure. Relatively stable, not easily affected by electromagnetic environment. Maxwell bridge is generally used as the electric bridge, and the capacitor and the measured inductance are in the opposite arm position.