AGC(automatic gain control) is used, namely, peak voltage of back wave signal after sampled is input to microprocessor, then A/D converter, D/A converter, gain control adjusting circuit to realize back wave signal AGC.

• 采用自动增益控制,即回波信号的峰值电压经过采样后进入单片机进行 A/D 转换,再经过 D/A 转换和增益控制电路,形成回波增益的自动控制;