TWL in-SITU tide gauge

The TWL in-situ tide gauge was designed by Tides and Water Levels of the Marine Sciences Directorate. It employs a single stainless steel capsule containing a differential potentiometric pressure transducer, temperature sensor, electrically operated valve and associated reference pressure system, electronics clock and timer, and a servo-operated Ott punch tape recorder along with a dry cell battery pack. Two gauges were tested on December 1971 outside Victoria Harbour at a depth of about 60 meters. Both the temperature and pressure were sampled at hourly intervals. The amplitude and phase of the tidal constituent computed from the data agree well with those obtained from the permanent gauge at Victoria. The design of the instrument was then modified to increase its reliability and depth capability. Three gauges were tested near Chebucto Head outside Halifax Harbour in May 1973. In this test, the sampling rate of the temperature was set at once a day while the pressure was once every hour. The differences in amplitude and phase of tidal constituents obtained from different gauges were larger than the results of the Victoria Test. This is probably caused by the inadequate sampling rate of the temperature data.