In situ water quality systems

The National Oceanographic Instrumentation Center performs extensive test and evaluation programs on many types of oceanographic and marine instrumentation systems. The purpose of the testing is to provide performance information on specific instruments for present and potential users, to encourage manufacturers in the development and production of reliable equipment and to create a focus of oceanographic instrumentation expertise which can be called upon by the community. One project at the Center has been the evaluation of water quality systems which combine several in situ oceanographic sensors integrated into a single package designed to measure parameters of interest in water quality studies. All of the systems included in this project measure conductivity, temperature, dissolved oxygen, and pH. One system also measures depth and produces a salinity output derived from conductivity and temperature measurements. In most cases, the basic techniques for sensing the various parameters are similar but sensor design varies. Most of the systems also permit the addition of optional sensors for other parameters and automatic data collection systems. All systems consisted of two separate units: an underwater sensor package and an electronic readout unit for placement on a dry platform. The two units are connected by means of either a single multiconductor cable or several individual and separate conductor cables.