DZSGRIPTICJ Idii) OPERATING IijdTRUCTIONS FOR 



viISZ GAGS'bH-1 



INTRGDbCTlON 



In the advancement of its research workj the Beach Erosion Board has 

 found it necessary to develop and utilize instruments that would accurately 

 measure and record the characteristics of ocean waves. Previously a step- 

 resistance staff gage has been developed in the laboratory of the Beach 

 Erosion Board (Technical Memorandum Noe 6, "An Ocean Wave Measuring 

 Instrument," published by the Beach Erosion Board in October 19)4.8) and al- 

 though installations of this type of gage have yielded valuable wave records, 

 its use has been somewhat limited due to the fact that it requires a 

 structure of some permanence on which to mount it. In order to obtain wave 

 records from localities xvhere no suitable structure is available for mount- 

 ing a staff gage^ an underwater pressure response type of wave gage has 

 been developed by modifying an earlier model of iiiis type developed by the 

 Woods Hole Institute of Oceanographyo Since a number of these gages have 

 been constructed at the Beach Erosion Board's laboratory for use by other 

 agencies, its description and operating instructions may be of interest to 

 recipients of this public ation. 



The Beach Erosion Board Type W.-1 wave gage consists of a pressure head 

 designed to detect pressure changes at a selected unden^ater location and 

 to convert the pressure change into a calibrated electrical signal which is 

 transmitted to the shore (or ship) by a 2~wire electrical cableo To the 

 shore end of the cable is attached a 11? volt, 60 cycle. General Electric 

 Photoelectric Recorder, equipped with a General Electric Fluxmeter sensing 

 unite The fluxmeter receives the electrical signal from the pressure head 

 and reacts to this signal in such a manner as to cause the Photoelectric 

 Recorder to draw a pen-and-ink trace of the pressure changes which occur 

 at the WH-1 pressure heado The construction and operating characteristics 

 of the equipment are given beloWo 



THE PRESSURE HEAD 



Figure 1 is a sketch of the WH-1 pressure heado Increased pressure 

 exerted on the outside of the large bellows, M, causes it to shorten in 

 length and compress the air between it and the small bellows, L. This 

 compression causes the small bellows to be elongated as a reaction to the 

 increased pressure. Attached to the small bellows is a solenoid suspended 

 in a high-density magnetic field; any movement of the small bellows gives 

 a corresponding movement to the solenoid. The action of the pressiire 

 head is such that the magnitude of the charge generated by the solenoid 

 varies directly with the pressure change imposed on the large bellows. 



A small diameter air leak connects the air chamber between the two 

 bellows, with the larger air chamber surrounding the small bellows and 



