n) Adjust 10-turn variable resistor clockwise until recorder 

 pen moves to full scale. 



o) Repeat steps j, 1, m, and n above. 



p) Place tide-capacitor switch to "in" position (switch open) 



q) Tide capacitor will begin to charge, and recorder pen 

 will slowly return to center of paper. When capacitor 

 has charged as indicated by recorder pen returning to 

 the center of the chart, quickly submerge the gage for 

 the remaining one-half value of maximum wave height ex- 

 pected. Recorder pen should again move to full scale on 

 recorder chart. Quickly move gage to a depth of 1 foot. 

 Recorder pen should move to opposite side of chart paper. 



r) To check gage linearity, place tide capacitor switch to 

 "out" position. Place gage in 1 foot of water. Move 

 recorder pen to side of chart paper with lever on side 

 of penmotor. Submerge gage in 1-foot steps for full 

 wave height. Slight adjustment of the 10-turn variable 

 resistor may aid in setting linearity and full scale. 



s) Record the dial reading on 10-turn variable resistor 

 and lock dial. 



t) Place gage in 1 foot of water. Re-center recorder pen 

 on strip chart. Place tide-capacitor switch to "in" 

 position. 



u) Gage calibration is complete; calibration may be plotted 

 on graph paper for further use. 



If facilities are available, calibration of the gage may be carried 

 out by using compressed air. Such facilities for calibration would in- 

 clude an airtight chamber for housing the gage. This chamber should be 

 large enough so that it does not mechanically hinder the gage bellows. 

 A precision pressure gage with a suitable source of compressed air and 

 air valves may be used to apply the same pressure to the air chamber as 

 would be developed by the water depth. Calibration procedures would then 

 be performed as outlined above, substituting equivalent air pressure for 

 water depths. 



b. Installation 



Consideration should be given to the type cable required 

 for use between the pressure-sensing unit and the recording equipment 

 located on shore. If the surf zone is of sand, it may be possible to use 

 4-conductor No. 14 AWG cable having a neoprene outer jacket. This type 

 of cable should be taped parallel to an ordinary 1/2" diameter steel 

 cable through the zone of wave action. The weight of the steel cable 



74 



