Most smart scales on the market are more convenient, and its measuring surface consists of four electrodes, so  four-electrical body fat solution is usually used. The signal generation circuit generates a sinusoidal current source as the excitation signal of the system applied to the two calls of the body through the electrodes, and then the other two electrodes collect the voltage on the two feet respectively. The four-electrical level body composition measurement model is shown in the figure on the right.