A deep-ocean electronic nephelometer

An electronic nephelometer which senses forward-scattered light as a measure of the concentration of particulate matter in deep-ocean water is described. The device consists of a light source and collimator, and a detection stage which uses a PIN photodiode, operational amplifier, correlation detector and a VCO. The VCO output is fed into the mixer of an STD system which transmits salinity, temperature, depth and light-scattering data to the ship via a cable-connected telemetry link for real-time analog and digital recording. Results of lowerings to 5600 m in the South Atlantic show a correlation between light-scattering profiles and the temperature/ salinity structure of western Atlantic Basin abyssal waters. Comparison is made between this instrument and a photographic nephelometer used routinely in the deep ocean.