Electronics Redesign of the NUS Model 1020 Hull-Mounted Sound Velocimeter.
Interim rept. Sep 81-Apr 83,
NAVAL OCEANOGRAPHIC OFFICE NSTL STATION MS
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The NUS model 1020 sound velocimeter is a hull-mounted device through which seawater is pumped at a rate of approximately three gallons per minute. The seawater sound speed is measured on a continuous basis to an accuracy of or - .15 meters per second ms over a range of 1400 to 1550 ms. The velocimeter is based upon the sing-around principle developed by C.E. Tschiegg and M. Grennspoan of the Nation Bureau of Standards. A pair of piezoelectric ceramic transducers and two reflectors are mounted to form a sound path of fixed length in the water. This sound path along with the transducers and associated electronic circuitry form the essential operating components of the sing-around circuit. During operation, a pulse of acoustic energy is transmitted through the water, received, amplified and used to generate another pulse of acoustic energy. The repetition frequency of this regenerative action is proportional to the transit time of the signal pulse and is therefore a measure of the sound propagation velocity. Errors resulting from the variations of water flow along the sound path length are minimized by folding the sound path. The redesign of the electronics in the NUS model 1020 hull-mounted sound velocimeter is described. Calibration test results are provided. The test data demonstrate that the redesign meets the accuracy specifications of the original instrument.