should cause the cable to sink well into the sand in the surf area. Slack 

 should be left in the cable to permit it to sink. 



If the cable must pass through a rocky (or impermeable) zurf zone, 

 it may be necessary to use armored cable through the area where wave 

 action will be directly on the cable. 



Cable used under water should be pressure-tested for leaks prior to 

 use. Most cable suppliers will make the pressure test when requested. 



The short length of cable attached to the pressure-sensing unit 

 should be spliced to the cable from shore using a 3-M No. 82A1 cable 

 splicing kit. 



The wave-sensing unit should be mounted to its support using the 

 plastic brackets shown in Figure 35. These brackets are required to 

 prevent galvanic action from corroding the sensing unit. The gage cable 

 should be taped firmly to the gage support at the point where the cable 

 leaves the brass gage case. If this is not done, wave action will flex 

 and break the cable. 



Laying the cable from the recording site to the offshore sensing 

 point requires planning based on the gage location on the seabed. Coiling 

 the cable in a figure 8 on deck of the boat, barge, or other vehicle will 

 allow the cable to pay out without twisting. It may be desirable to lay 

 the cable, and then splice the gage to the end after it is in place. The 

 splice requires about 30 minutes to harden before placing under water. 



After the gage is in its operating location and the cable laid to the 

 recording site, install the amplifier-power unit, the strip-chart recorder, 

 chart rewind, programmer, and magnetic tape recorder (if used) and connect 

 them as shown on Figure 40. The color code of the leads from the Sanborn 

 linear differential transformer must be carried to the corresponding 

 binding posts on the amplifier-power unit. 



After the gage system is connected as outlined above, apply power to 

 the amplifier-power unit, strip-chart recorder, and magnetic-tape recorder, 

 chart rewind, and the gage is ready for operation. The 10-turn variable 

 resistor dial should be set to the value obtained in the calibration pro- 

 cedure, and the tide-capacitor switch should be set in the "in" position 

 (switch open) . 



When the gage is first placed in operation, the recorder pen will 

 probably be off scale, since the tide capacitor is not in a charged 

 condition. The off-scale condition of the recorder pen is normal, and 

 the pen will slowly return to its normal position (center of chart) as 

 the tide capacitor charges. The tape recorder signal meter will also be 

 off scale as outlined above until the tide capacitor charges. 



The programmer should be adjusted to provide the desired wave-record 

 program. The programmer will start the record at the beginning of each 



75 



