Salinity-temperature-depth recorder for sea water

MANY physical phenomena in the oceans can be determined from measurements of the horizontal and vertical gradients of salinity and temperature. The “salinity-temperature-depth recorder” was developed to permit these measurements to be made continuously from a moving vessel. This type of instrument has been operated regularly for several years and has been found useful for obtaining hydrographic data. It has been applied particularly for inshore surveys in shoal water and in ocean areas where its accuracy of 0.2 degree Fahrenheit and 0.3 part per thousand (‰) salinity are adequate. The instrument measures temperature over the range from 28 to 90 degrees Fahrenheit and specific electrical conductance from 0.00 to 0.07 mho, and from these computes salinity. Depth is measured over the range from 0 to 1,200 feet. The measured depth and temperature and the computed salinity are recorded simultaneously on a linear strip chart. The instrument operates from a 115-volt 60-cycle supply and is unaffected by normal variations in voltage and frequency and by the motion of the vessel.