Principle model of lcr bridge

With the development of modern analog and digital technology, especially the development of high-speed operational amplifier and microprocessor technology, modern impedance measurement mostly uses the automatic balanced bridge method, as shown in the following figure:

In the above figure, firstly, a sinusoidal AC signal with a certain frequency and amplitude is generated by the signal source, which is added to the DUT to generate a current that flows to the virtual ground "V". Since the input current of the operational amplifier is zero, the current flowing through the DUT completely flows. Because of the introduction of virtual ground function of operational amplifier, the accuracy and anti-interference ability of this measurement method have made a qualitative leap.

of course, the above is only an abstract principle model, and the real product is much more complicated.