I INPUT/OUTPUT FITTINGS! 



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FLASK PRESSURE INDICATOR! 



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FLOW METER 



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Fig 9 12 A flow meter and flask pressure indicator once used aboard ALVIN. but now replaced. (WHOI) 



tern shown in Figure 9.13. This unit (model 

 202) reads from 0-100 percent oxygen or 0-1.0 

 absolute atmosphere of partial pressure. The 

 oxygen is sensed directly by a galvanic cell 

 containing a gold cathode and a lead anode 

 in a basic electrolyte. Oxygen diffusing 

 through the cell face initiates redox reac- 

 tions which generate a minute current pro- 

 portional to the oxygen's partial pressure. A 

 remote sensor in the diver chamber allows 

 the pilot to monitor either sphere or diver 

 chamber oxygen concentrations. 



The oxygen sensor in DS-4000 was de- 

 signed by Mr. Alan Krasberg in 1962 and 



operates on the principle of a fuel cell. When 

 molecules of oxygen impinge on the sensing 

 element, a voltage is generated which is pro- 

 portional to the partial pressure of the local 

 oxygen concentration. This device indicates 

 continuously on a 0-50 percent dial where a 

 green ring spans the desired 17 to 25 percent 

 range. The unit operates routinely off the 

 main power supply (28 VDC drawing 0.1 

 amp), but in a power failure it has its own 

 batteries which are kept charged by the 

 main supply. The device is shown in Figure 

 9.14. Its accuracy is within the order of its 

 readability, ±0.2 percent. 



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