changing temperature on the electronic circuitry. A provisional method 

 for doing this by determining the time constant has been discussed 

 with the Instrumentation Division of this Office. 



It is recommended that the proposed calibration facility include 

 provisions for rapidly testing such devices over the range of tempera- 

 tures and pressures encountered in normal oceanographic work. 



It also has been recommended that the Instrumentation Division 

 conduct an evaluation test of strain gauges for pressure measurements, 

 an application for which no specific information was available to the 

 Committee. (Strain gauges have, however, been used in recording 

 harbor surge.) 



Because of their simplicity, Bourdon tubes probably will be used in 

 shallow depth determinations for some time, despite their questionable 

 accuracy. Recent field tests of these were inconclusive. 



The sonar pinger system should be evaluated for Hydrographic 

 Office use. 



H. CURRENT MEASUREMENTS 



Although it lacks many desirable features, the Roberts Current 

 Meter is the instrument most depended upon by the Hydrographic 

 Office for measuring ocean currents. Steps have been taken to im- 

 prove its accuracy, lower its threshold speed, and simplify the data 

 record. However, even with such improvements, the Roberts Meter 

 cannot be regarded as a totally satisfactory general purpose current 

 meter. 



Recent developments which are currently under test by the Hydro- 

 graphic Office include: (1) the adaptation of the electromagnetic log 

 to measure currents, (2) an instrument employing two-way doppler 

 as the basis for measuring water flow, and (3) the Snodgrass meter, 

 which employs an extremely sensitive Savonius rotor and generates 

 an FM signal. 



The use of simple strain gauges for deriving current speeds from 

 forces exerted on spheres or flat plates appears to be very promising. 

 Crude models of such instruments have been assembled and tested by 

 the Hydrographic Office with encouraging results. Because of the 

 encouraging prospects indicated at modest cost, it is recommended 

 that this work be continued within this Office to prove further the 

 soundness of the concept and that a contract then be let for the con- 



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