Daowan DW16 series CTD is used to measure the three basic physical parameters of conductivity, temperature, and depth. According to these three parameters, salinity, sound speed and density of seawater can be calculated, so that the distribution of ocean temperature field and sound field can be observed. CTD is the most critical and basic measuring instrument in ocean survey and research, such as hydrology, physics, chemistry, geology, biology, etc. And essentially in marine economic development, marine observation, and marine national defense construction. The maximum operating water depth is 7200 meters.