of water flov; v;ere made for the new coil, which imder some conditions ex- 

 caeddd the jnln^atod value of the cteraically prdd'ucad voltage, 



"^'iiQ t-'Gveral types of electrodes used for these tests are as folloivs: 



a. 22 gauge bare copper vrire 



b. 1/4 inch bare copper tubing 



c. 3/3 inch bare copvjer tubing 



d. 1 inch copD3i- di.soE, formed from capillpry tubing 



e. 22 gayge .u-chrome wire 



f . 22 gauge bare copper shaet, exposed surface 1-g- inches by 



1/4. inch 



g. 22 gauge tantalum wire 



h. 17 gauge titanium plate, exposed surface 1 inch by I/4 inch 



No satisf.ajbory measurements could be made utilizing the 22 gauge Dare cop- 

 o-;-.' o.^ nlchroirie Yri.ro j1 jctrodes. A potential always existed across 

 thase v^ire electrodes which completely obscured any vrater velocity -in- 

 dujj 1 voltasjc. rha uloctrodes made up of copper tubing and those shaped 

 as discs were discarded because they obstr ictod the flow of water and 

 created turbulence which resulted in ■,.l]<ily fluctuating readings on 

 the recorder. It was recognized that the vfire electrodes had a terminal 

 resistance much higher than the resistance value recommended to be 

 connected with the recorder. The operating recorder requires a small 

 current from the measured potential, and it is believed that this fact 

 combired with the varying electrolytically-induced potential prevented 

 the recorder from reaching a balance and recording the velocity-induced 

 quantity. Electrodes fashioned from the highly corrosion resistant 

 metals of tantalum and titanium were also unsatisfactory. The limited 

 action between the water and electrodes resulted in a high circuit 

 resistance and no satisfactory readings could be taken. Several ad- 

 apter circuits developed for use between the ele.;t'odes and the recorder 

 were testqd, but proved unsatisfactory, 



Eff'oi'^s" directed toward reducing the terminal resistance of the 

 electrode's resulted in the use of the copper sheet electrodes, and with 

 this type the velocity-induced voltage produced vrhen the coil'Viras 

 energized, could be clearly observed on the recorder as superimposed 

 upon the changing reading of the potential produced: by ©lectrolytic 

 action. It was shown that in the presence of the magnetic' field, a, 

 voltage was induced in the flowing water that was aidirect but; no^i- 

 linear function of the water velocity. The salinity of the v^ate^r had 

 no apparent effect on the relationship between velocity and ^t he induced 

 voltage. 



Before a practical instrument utilizing the principle of electro- 

 magnetic induction can be developed to measure 'and record water 

 velocities satisfactorily, it appears that a. suitable means of eliminat- 

 ing or compensating the chemically induced voltage must be found. An 

 instrument built for continuous operation must also overcome the basic 



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