where 



H(j s c^amic head in feet of sea water (density 1.035) 



K = attenuation constant {^p/^Po ) taken from the curve 

 (Figure 7). Based on d (depth) and T (wave period), 



H^ = wave height in feet of sea water. 



The gage is calibrated with the recorder so that a dynamic head of 

 1 foot of seawater produces a deflection of the recorder pen of 2 (or 

 sometimes 3) vertical divisions on the GE chart paper (See Figure 8). 



CIRCUIT CHECKS 



The resistance of the gage circuit, measured at the end of the 00 

 feet of cable attached to the gage should read approximately 7 ohms 

 (+ 1 ohm) with an accurate ohrameter. When a resistance check is made with 

 additional connecting cable attached, allowance for the cable resistance 

 should be made. If the resistance is less than expected, leakage through 

 the cable entrance cap can be suspected. If salt water has entered this 

 connection gland, it should be washed with fresh water and dried. After 

 this operation has been performed, the resistance between either conductor 

 and the gage case should be above one-half megohm. Resistances as low as 

 10,000 ohms between either conductor and the gage case will not cause any 

 detectable variation in performance* 



The operation of the gage can be checked before placing it in operation 

 by using a vacuum-tube-voltmeter. The voltmeter is connected to the ter- 

 minals of the gage, and with the voltmeter set on a lo^-voltage range, the 

 bellows are rapidly compressed by hand, A slight flickering of the volt- 

 meter needle indicates satisfactory* output from the gage. 



After the gage has been placed in operation in water, the resistance 

 between either gage cable conductor and the water should remain the same 

 as it was between either conductor and the gage case. However, if the 

 resistance between either conductor and the water has fallen an appreciable 

 amount, leakage should be suspected. If the output as measured on the 

 recorder starts dropping off, the cable should be replaced. If the 

 resistance between either conductor and the water is low, but the reading 

 from one conductor to water is slightly more than from the other conductor, 

 the cable is probably short-circuited through only one conductor to water, 

 and the cable is still satisfactory for use. 



When the above tests show the gage to be satisfactory, but the recorder 

 does not give a record, the recorder shoiild be examined for malfunctioning. 

 The instruction book will give assistance for trouble -shoo ting. By removing 

 the recorder from the case and watching the galvanometer mirror move (with 

 gage operating) the trouble can be isolated. If the mirror is moving, but 

 the pen does not, the trouble is probably in the amplifier. If the mirror 

 does not move the trouble is in either the galvanomel^er or the gage circuit, 



10 



