usually is located in a relatively exposed posi- 

 tion. It must be kept dry and clean as it is 

 likely to be the principal source of instrument 

 failure. 



9-33 The Recorder.— Both routine and 

 special maintenance for the recording unit 

 are described in detail in the operating and 

 maintenance manuals supplied by the man- 

 ufacturer for the instrument. 



9-34 COMPUTING THE CURRENT 

 FIX. — It is usually unnecessary to process the 

 data aboard ship. In the event that the 

 results of a current fix are required at sea for 

 special studies, they can be obtained by 

 completing oceanographic log sheet GEK 2 

 in accordance with the instructions given in 

 chapter 14. 



9-35 STORING AND SHIPPING REC- 

 ORDS AND DATA.— Each used chart roll 

 should be placed in its container and plainly 

 marked with the ship's name, cruise number, 

 dates of the beginning and end of the chart, 

 and the roll number. The associated ocean- 

 ographic log sheets GEK 1 and 2 should be 

 placed in a manila envelope and similarly 

 marked. At the end of a cruise, these records 

 should be forwarded along with the other survey 

 data to: 



The Hydrographer 



U. S. Navy Hydrographic Office 



Washington 25', D. C. 



Attn: Code 5430 



9-36 SUMMARY OF IMPORTANT 

 POINTS. — To insure proper operation of the 

 GEK, always be certain that: 



1. The distant electrode (black lead wire in 

 the electrode string) is connected to the positive 

 input terminal (sec. 9-8). 



2. The dry cell in the recorder is in good con- 

 dition. 



3. The junction box is dry and its contact 

 bright. 



4. The cable is plugged in properly at the 

 junction box when the instrument is in opera- 

 tion. 



5. The recorder is not stopped for an extended 

 period with the automatic current adjuster in 

 the operating (standard cell) position. 



9-37 INSTRUCTIONS FOR OPERATING 

 THE EKMAN CURRENT METER.— The 

 Ekman current meter was developed by Dr. 

 V. Walfrid Ekman, a Swedish scientist, whose 

 origiTial design, although modified, remains 

 basically unchanged. Tlie meter is designed 

 to give speed and direction of the current at any 

 depth. It consists of an impeller or screw, and 

 shaft connected to a set of dials. The number 

 of shaft revolutions per unit of time is read from 



the dials on the main body of the meter. A 

 reservoir of bronze balls is connected by a nar- 

 row tube to a compass box containing a compass 

 needle. Below the needle is the compass-ball 

 receptacle which is divided into 36 chambers, 

 each representing 10° of azimuth. As the im- 

 peller rotates, the balls fall, one at a time, onto 

 the top of the compass needle which guides them 

 into one or another of the chambers, depending 

 on the heading of the current meter. This 

 gives the direction toward which the current is 

 flowing. 



The current meter is lowered on either the 

 oceanographic or bathythermograph wire. The 

 impeller is locked while lowering or hoisting. A 

 messenger is sent down the wire to unlock the 

 impeller and set the meter in operation. A 

 second messenger is sent down to lock the im- 

 peller and stop the meter before hoisting (fig. 

 9-3). 



Figure 9-S. The Ekman current meter. 



Valid measiu-ements cannot be made with an 

 Ekman current meter unless the ship or buoy 

 from which it is suspended is anchored. 



Instructions for operating the Ekman current 

 meter are given in the U. S. C^oast and Geodetic 

 Survey Special Pub. No. 215, Manual of Current 

 Observations. They are given briefly here. 



9-38 The Carrying Case, Spare Parts, and 

 Accessories for the Ekman Current Meter. — 

 The components, spare parts, and accessories 

 for the Ekman current meter are contained in a 

 carrying case. When assembling a meter, care 

 must be taken in removing parts from the case. 

 All parts must be checked before assembling 

 the meter. After completing a current survey, 

 each part must be removed from the body of the 

 meter and thoroughly rinsed in fresh water be- 

 fore returning it to the proper compartment in the 

 case. In addition to the main body of the meter. 



92 



H. O. 607 



