of water flovr vrere made for the new coil, which under some conditions ex- 

 caed^jd the jnli' eatod value of the chemically pix»duced voltage, 



'^ha several types of electrodes used for these tests are as follow's: 



a . 22 gauge bare copper vd.re 



b. 1/4 inch bare copper tubing 



c. 3/S inch bai'e cop^jea- tubing 



d. 1 inch copp3r discs, formed from capill?ry tubing 



e. 22 gauge iiichrome wire 



f . 22 gauge bare copper shaet, exposed surface I2 inches by 



1/4. inch 



g. 22 gauge tantalum wire 



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



No satisfaobory me^ surements could be made utilizing the 22 gauge oare cop- 

 o'.iv or nichrome Yfi.x':: ;2ljc:trodes. A potential always existed across 

 these wire electrodes rrtiich completely obscured any v;ater velocity -in- 

 duoj 1 volta[;io. rha el.jctrodes made up of copper tubing and those shaped 

 as discs were discarded because they obstr-^ctod the flow of water and 

 created turbulence which resulted in -..ildly fluctuating readings on 

 the recorder. It was recognized that the v/ire 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 

 combined with the vairying 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 tantal-um 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 tested, but proved unsatisfactory, 



Effp^'^s" directed toward reducing the terminal resistance of the 

 electrodes resulted in the use of the copper sheet electrodes, and with 

 this type the velocity-induced voltage produced when the coil vras 

 energized, could be clearly observed on the recorder as superimposed 

 upon the changing reading of the potential produced: bjy electrolytic 

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

 voltage was induced in the flowing water that was a'djrect but; no^i- ;, 



linear function of the water velocity. The salinity- of the v^atqr had 

 no apparent effect on the relationship between velocity and '^the 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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