An automated profiling water quality sensing system

An automated profiling system has been developed for obtaining water quality data in the upper 100m of the water column. Designed for unattended operation from remote battery-powered platforms such as telemetering buoys, the system requires as little as 1.5 A-h of energy for a 15 minute deploy-retrieve cycle.Parameters sampled during a profiling sequence are depth, temperature, conductivity, dissolved oxygen, pH and transmittance. System hardware includes a sensor package, electro-mechanical cable, winch, winch controller, sensor readout unit, and data processing/control electronics. The microprocessor-based data processing/control electronics provides considerable flexibility in selection of operating modes. The stored program has provisions for selecting more than 10 different profiling scenarios which include combinations of sampling depths and data averaging times. Data are averaged and stored in BCD format and are scaled in physical units. The data output interfaces with either RF telemetry equipment or magnetic tape recorder. In order to minimize energy requirements for battery operation, a computer simulation was performed for defining system component performance characteristics. Variables in the simulation included sensor size and weight, cable diameter and specific gravity, winch drum width and diameter, winch motor speed-torque characteristic and drive train reduction ratio. Results of the trade-off study are presented and estimated system performance is compared with test data. Results of sea tests conducted off the California coast are presented. Based on the demonstrated performance, a telemetering buoy as small as 6m in diameter can support system operation with a battery power supply for one year. A long-term operational deployment from a telemetering buoy is planned to begin in October of 1977.