A compact 7 parameter oceanographic probe

In response to the increasing need for accurate and reliable water quality monitoring instrumentation, we have directed our research and development efforts toward the measurement of chemical and biologically related parameters in addition to the classical physical measurements of conductivity, temperature, and depth. The Model 513 Oceanographic salinity, temperature and depth instrument was used as the starting point for the addition of Dissolved Oxygen, pH, Turbidity, and Specific Ion sensors. The systems integration problems and sources of error in measuring these parameters is the main focus of this paper. Long term results for unattended dissolved oxygen measurements show an average error of 0.05 PPM over a 22 day test period without any recalibration. Long term errors for other parameters are less.