assembly should be placed in the linear differential transformer and 

 placed in the gage barrel. Plastic washers must be placed between the 

 transformer and the bottom of the barrel. These washers must be of 

 varying thicknesses. The electrical output of the transformer should 

 be zero or slightly negative when the transformer is resting on the 

 washers in the gage barrel. 



Connect the differential transformer to a 6-volt d.c. source and 

 measure the output with a high-impedence voltmeter set on a low range - 

 about 3 volts. With the steel ball in contact with the magnet in the 

 bellows chamber, with the bellows in free air (no pressure), and the 

 transformer in firm contact with the plastic washers, the voltmeter 

 should read volts, or slightly negative. Pressing the bellows with 

 the fingers should show an upscale (positive) movement of the voltmeter. 

 If the zero or slightly negative output voltage is not obtained on first 

 trial, then the transformer and core assembly must be removed from the 

 gage barrel and plastic washers of a different thickness tried until the 

 correct reading is obtained. After the correct washers are selected, 

 put together the spring assembly and "0" ring, and solder the transformer 

 leads to the leads in the epoxy sealed cable-end of the gage housing. 

 Fasten the cable portion of the gage housing to the gage barrel, using 

 6 No. 10-32 screws. These screws should be tightened a little at a time 

 to ensure equal pressure on all sides of the "0" ring seal. 



Fabricate the amplifier, power-supply unit as shown in Figure 37; 

 wire the unit according to Figure 38. 



Construct the programmer by installing three 115-volt receptables, 

 toggle switch and line cord on the timer as shown on Figure 10. 



Change the chart speed on the strip-chart recorder (if desired) as 

 outlined in Section VIII. 



Fabricate a signal cable for the strip-chart recorder of the desired 

 length using 2-conductor No. 18 AWG cable and connectors as shown on 

 Figure 11. 



Fabricate a suitable underwater mount for the pressure unit. This 

 mount should be high enough to keep the gage free of the ocean bottom; 

 it should be large enough and heavy enough to remain in an upright posi- 

 tion during periods of heavy wave conditions. To prevent metal erosion 

 caused by galvanic action, dissimilar metals should not be used in contact 

 in sea water. The brass pressure-unit must be mounted in plastic insulat- 

 ing brackets to prevent metal erosion by galvanic action. Lifting eyes 

 should be provided to lower the mount to the ocean floor and for attaching 

 a marker buoy .(if required) . A simple concrete mount has been used for 

 the gage in some locations (Figure 39) . If a marker buoy is used, the 

 gage should be protected from the sagging and twisting of the buoy cable. 



69 



