A temperature-chlorinity-depth recorder for use at sea

An instrument for recording temperature, chlorinity and depth in the upper 1000 metres of the sea is described. The temperature range is 0-30° C, with an accuracy of ±0 15° C. The chlorinity range spans about seven parts per thousand of chlorinity, the accuracy being ±0.03 parts per thousand. The accuracy in depth is ±10 m. The three quantities are recorded sequentially by a single-pen strip-chart recorder, each quantity being recorded for five seconds at a time. The underwater unit is suspended by means of an armoured steel cable, which has a single electrically-insulated core. This core carries power down to the underwater unit, and brings up the signals from the measuring elements. A simple frequency-modulation method of telemetering is used.