U.S. NAVY OCEANOGRAPHIC INSTRUMENTATION CENTER 



NSTRUMENT 



I ACT 



MAY 1964 



TFS-nni-fi4 



This document is issued to acquaint users of oceanogrophic instruments with the technical results 

 of engineering evaluations conducted in the laboratory and the field by the Instrument Center. 



PEEP SEA VELOCIMETEi 



MODEL 



TR-4-A 



MANUFACTURER 



ACF INDUSTRIES 



DESCRIPTION 



THE TR-4 VELOCIMETER IS A SELF-CONTAINED INSTRUMENT 

 DESIGNED TO DIRECTLY MEASURE THE VELOCITY OF SOUND 

 IN WATER USING THE "SING-AROUND" TECHNIQUE. AN ACOUS- 

 TIC PULSE IS TRANSMITTED THROUGH THE WATER AND WHEN 

 RECEIVED, TRIGGERS ANOTHER TRANSMITTED PULSE. THUS, 

 THE RESULTING REPETITION RATE (I.E., FREQUENCY) IS PRO- 

 PORTIONAL TO THE SOUND VELOCITY. THE FREQUENCY SIG- 

 NAL, AFTER TRAVELING THROUGH THE NECESSARY CABLE 

 LENGTH IS THEN AMPLIFIED AND DOUBLED BY THE AUXILIARY 

 FREQUENCY DOUBLER. 



This Instrument Fact Sheet does not constitute on endorsement of ony commercial product or conclude any 

 procurement action or intend to be an opinion beyond engineering or technical fact by the U. S. Navy. 



