The system with signal peak voltage holding, A/D converter, microprocessor, D/Aconverter and voltage adjustment was introduced to realize the ultrasonic signal AGC.

• （3）采用自动增益控制，即信号的峰值电压经A/D变为数字信号送给单片机，再通过D/A和电压调节电路调节增益控制电压，实现测量信号的自动增益控制。