3. Operation of Parallel-type, Step-Resistance Gage 



a. Installation 



Install the metal gage holder at the operation site. The 

 holder should be installed so that about 6 to 8 feet are below mean lower 

 low water and 17 to 19 feet out of the water. 



Provide a mounting for the transformer unit near the top of the gage 

 mount but do not mount the transformer unit at this time. 



Install the 4-conductor No. 14 AWG cable between the gage holder site 

 and the recorder site. 



Install the epoxy gage sections in the mount. 



Install the voltage-control programmer unit, the strip-chart recorder, 

 chart take-up and magnetic tape recorder (if used) at their operating site. 

 Connect these units and the transformer unit to the gage sections as shown 

 on Figures 23 and 24. 



b. Calibration 



The accuracy of the recorded wave heights depends directly on 

 the accuracy of the calibration of the gage. There are enough differences 

 in each wave gage and each strip-chart recorder to require that each gage 

 be individually calibrated. 



The ideal calibration would be that of raising and lowering the steel 

 gage holder with the gage sections into the water in small increments and 

 marking the strip-chart recorder accordingly. Usually, the lack of water 

 depth, the manual process required, and the presence of wave action prevent 

 such calibration. 



If many gages are to be calibrated, it may be desirable to provide a 

 water basin about 24 inches in diameter with the required depth. A wave 

 gage holder would be a permanent part of the calibration pit. The basin 

 should be made of concrete pipe or other nonconducting material; use of 

 a metal wall would cause inaccurate calibration of the gage. Water with 

 proper salinity would be required. 



The procedure outlined below has been used and found satisfactory for 

 calibration of staff -type gages. If feasible, a time of low wave action 

 should be selected. 



If possible, keep the sections to be removed from the water first in 

 the calibration process inside the steel gage holder. This will provide 

 a more accurate gage calibration. If the water is deep enough, place two 

 or three of the sections in the holder in the order that they are used in 

 the gage. The section having the lowest value of resistors is on top, and 



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