This paper designs and realizes a low-power and high-resolution
OBS sampling unit which can adopt 4-way synchronous sampling signals and store data in SD card. What’s more, the system extends USB Host interface to connect with mobile hard disk in order to store data when there is a long time sampling. It realizes the two characters of low-power and dynamic range by carefully design its hardware structure and software digital signal processing algorithm. This sampling unit finally realizes dynamic range about 120dB and when sampling ratio is less than 1Ksps and the power is less than 250mW which ensures that battery can work long time undersea. Multiple trials verify the performance of sampling unit and compare its data with standard sampling device data. Experimental results demonstrate that the system utilizing over-sampling technology can improve dynamic range of signals. Besides, it verifies the reliability and practicability of the system by sampling of sound explosion signal further according to sea trials.