CTD (Conductivity, Temperature, Depth) Profiler

Abstract

One of the most useful instruments developed for determining seawater properties during the last four decades has been the CTD (conductivity, temperature, depth). This device has supplanted the traditional hydrocast using Nansen bottles and reversing thermometers that was standard physical oceanographic practice from about 1910 to 1970. The CTD, although an electronic instrument, has its origin in the older technology. The computations of properties such as depth, salinity, density, speed of sound, and potential temperature have been greatly facilitated by having the measurements of conductivity, temperature, and pressure in digital format for direct entry into standard formulas, originally in FORTRAN but now in Matlab and other computational engines.