ABSTRACT 



This report describes a dynamic wave-height recording 

 system which utilizes an insulated wire probe as a 

 capacitance-type transducing element . The electronic portion 

 of the system is designed as a plug- in component of a 

 commercial direct-writing recorder console. The output of 

 the system is in the form of a rectangular plot of wave 

 height versus time,, Schematic diagrams and operating 

 instructions are included. 



INTRODUCTION 



In a facility engaged in ship hull design, the problems 

 associated with the testing of the various models in waves 

 dictate that some types of tests be made in waves of known 

 and controlled dimensions. The waves desired for these tests 

 may be produced by the various wavemakers available at the 

 David Taylor Model Basin, It is desirable to be able to 

 record these wave profiles and produce a permanent record 

 for analysis and correlation with other data. Furthermore, 

 such a record allows the wavemaker to be more easily adjusted 

 to the desired condition. 



In earlier work, some wave profile recording was done 

 by photographing a grid marked on one wall of the basin. As 

 the wall had an adverse effect on the wave shape, and as 

 any imperfections in the wall surface further distorted the 

 wave, the method left much to be desired. Also, the results 

 were not available until after the film was developed. 



During 1952 5 the TMB Type 145-A Dynamic Wave-Height 

 Recorder" 1 was designed and produced and has met with notable 

 success in a number of tests since that time. This system 

 exhibited excellent linearity characteristics, and the gage 

 was easy to produce and simple to clean or replace when 

 necessary. No photography was required, and the gage 

 dimensions were small enough to cause little effect on the 

 wave under investigation. 



In order to meet the needs of the expanding test programs 

 of the Hydromechanics Laboratory, more channels of wave-height 

 recording instrumentation were desired. In the meantime, a 

 commercial direct-writing recording system featuring semimodular 

 construction became available. It was decided to redesign the 

 circuits of the older Type 145-A recorder and package the 

 electronic portion in a plug-in chassis which could be used 

 with the new recording console. All the_ desirable features 



_1 References are listed on page 19 



