SOLDER 



SOLDER 



0.020 S. S. 



— O.R. 



1.625" BAR STOCK" 



1/8" PLATE BRASS 



O.R. 



DEAD SPACE 

 FLUID ISOLATOR 



— iwff LX 1601AF 

 PRESSURE 



TRANSDUCER 



SWAGELOCK O-SEAL MALE 

 CONNECTOR B-300-1-20R 



FIG. 2a Detail of mounting of pressure transducer in Swagelock 

 fitting and brass insert. The latter is most easily constructed by 

 first machining the bar stock to correct dimensions and then 

 adding the 1/8 in. plate. The center adapter of the Swagelock 

 fitting can be machined from 1/4 in. brass rod and the 0.020 s.s. 

 capillary soldered inside it. 



FIG. 2b Circuitry showing battery operation: Reg.; LM 340-15 

 National Semiconductor 15 volt regulator; SI. three position 

 switch for on/off and battery or regulated voltage reading; R1, 

 2000 ohm 10 turn helipot; R2, 5000 ohm 10 turn helipot. R3, 

 2000 ohm (1/4 watt) resistor; P D , pressure transducer; V , jacks 

 where output or battery voltage is measured. 



A< R R 1 

 R 2 



B< R 1 

 R 2 



c< R i 



2 



660 

 502 



827 

 747 



948 

 933 



AMBIENT PRESSURE 



mm Hg 

 200 

 150 

 100 

 50 ./// 



1.5 1.0 



/.M 50 



I ■ 



./a 



/ 



/ 



dV 

 dP 



0.5 1.0 1.5 



+ VOLTS 



100 



150 

 I 200 



10 mV 

 mm Hg 



REMOVAL 

 136% SAT'N 



FIG. 2c Alternative calibration slopes for V„. A, to read in 

 mm Hg where 1 mm Hg = 10 mV; B, to read in inches of mercury 

 where 1 in. mercury = 100 mV and inches of mercury = V x 10; 

 C, to read in percent supersaturation where 10% supersaturation 

 = 100 mV, the percentage excess of undersaturation = V x 100. 

 The latter calibration "throws away" most of the pressure sensi- 

 tive output and is accordingly less accurate. 



FIG. 2d Recording of approach to maximum reading taken in 

 the N.M.F.S. Montlake Laboratory in Seattle. Final pressure mea- 

 sured (referred to surface) was 136% saturation reached in 7.5 min 

 and was reproduced in three consecutive trials. Notice the more 

 rapid return to equilibrium following removal of the probe 

 because of the physically different (gas/membrane/gas) diffusion 

 situations. 



which does not occlude the lumen of the tube and 

 the other end is attached to the protruding end of 

 the stainless steel capillary. The hair curler is 

 fastened (with a hose clamp) to the machined end 

 of a PVC pipe plug which threads directly into the 

 PVC union. A cylinder of perforated metal is in 

 turn hose-clamped directly to the latter to protect 

 the silastic tube. This construction facilitates carry- 

 ing several prewound "spare membranes" in field 

 studies so that replacement, if necessary, can be 

 accomplished in minutes. 



The terminals of the pressure transducer are 

 connected to the waterproof three-wire neoprene- 

 covered cable (Belden 19229, 18-3 SJO Rancho- 

 prene®) by constructing a small five-wire clip 

 from one side of an in-line integrated circuit IC 

 socket. Only the ground (pin 2), supply (pin 5) and 

 output (pin 1) terminals of the chip are used in this 

 configuration and are connected to the cable by 

 5 in. of small flexible #20 hookup wire. The cable 

 attachment to the PVC union is both waterproofed 

 and strain-relieved by means of a plastic cord grip 



708 D'Aoust, White, Seibold 



