ST (CA ee ieee AD CERC WAVE GAGES by Leo C. Williams DATA LIBRARY & ARCHIVES Woods Hole Oceanographic > inatitution TECHNICAL MEMORANDUM NO. 30 DECEMBER 1969 U. S. ARMY, CORPS OF ENGINEERS © COASTAL ENGINEERING - RESEARCH CENTER — _ This document has been approved for public release and sale; its distribution is unlimited. Reprint or republication of any of this material shall give appropriate credit to the U. S. Army Coastal Engineering Research Center. Limited free distribution within the United States of single copies of this publication is made by: Coastal Engineering Research Center 5201 Little Falls Road, N.W. Washington, D. C. 20016 Contents of this report are not to be used for advertising, publication, or promotional purposes. Citation of trade names does not constitute an official endorsement or approval of the use of such commercial products. The findings in this report are not to be construed as an official Department of the Army position unless so designated by other authorized documents. CERC WAVE GAGES by Leo C. Williams TECHNICAL MEMORANDUM NO. 30 DECEMBER 1969 0 0301 0045172 O U. S. ARMY, CORPS OF ENGINEERS COASTAL ENGINEERING RESEARCH CENTER HN AAU This document has been approved for public release and sale; its distribution is unlimited. ABSTRACT CERC has used wave gages to gather prototype wave data since 1948. Two basic types of gages are now used in the field - the step-resistance staff gage and the underwater pressure-sensitive gage. CERC has developed three types of step-resistance staff gages - a series type for use in fresh water, a parallel type for use in salt water, and a relay-operated type for use in either fresh or salt water or in water where wide changes in salinity occur. The pressure gage can be used in water of any salinity. The series and parallel gages have an accuracy of +5 percent plus the spacing of one sensor increment. The relay gage has an accuracy of +2 percent plus the spacing of one sensor increment. The accuracy of the pressure-sensitive gage is not as precise as that of the step-resistance gages. The report describes each gage and the theory of operation, details of fabrication, steps for calibration and installation, and requirements of maintenance. FOREWORD This report describes in detail the sensors and recorders used by CERC in wave-data collection programs. Leo C. Williams, Chief of the Instrumentation and Equipment Branch, Research Division, prepared this report and developed most of the wave-data equipment used at CERC. Thorndike Saville, Jr. is Chief of the Research Division. The Manuscript was prepared in 1966. Many drawings in this publication have been greatly reduced from the originals. The large originals are available at CERC in limited quantities. At the time of publication, Lieutenant Colonel Edward M. Willis was Director of the Center; Joseph M. Caldwell was Technical Director. NOTE: Comments on this publication are invited. Discussion will be published in the next issue of the CERC Bulletin. This report is published under authority of Public Law 166, 79th Congress, approved July 31, 1945, as supplemented by Public Law 172, 88th Congress, approved November 7, 1963. Section Io ae 3. Section ile Oe 3. Section 1. De 3 Section rom Section il 2 Bo Section Section ily De Sg Section Section IN Ox. CONTENTS I. INTRODUCTION . Wave Program at CERC ..... . Recording and Analysis Types of Wave Gages II. SERIES-TYPE, STEP-RESISTANCE GAGE FOR USE IN FRESH WATER . STO PRE auals Hoe, MEPS eCKe) aes hob Theory of Operation of Series-Type, Step-Resistance Gage Fabrication of Series-Type, Step-Resistance Gage Operation of a Series-Type, Step-Resistance Wave Gage . III. PARALLEL-TYPE, STEP-RESISTANCE GAGE FOR SALT WATER . Theory of Operation of Parallel-Type, Step-Resistance Gage Fabrication of a Parallel-Type, Step-Resistance Gage Operation of Parallel-Type, Step-Resistance Gage IV. RELAY-TYPE,STEP-RESISTANCE GAGE FOR SALT AND FRESH WASTE Ro camer omerce omc camsiuet ghallshn “oy tralia Sec titers eM ere arate \eetan ea rcimige ate a Theory of Operation of a Relay-Type, Step-Resistance Gage . Fabrication of a Relay-Operated Step-Resistance Gage Operation of a Relay-Type, Step-Resistance Gage . V. PRESSURE-SENSITIVE GAGE Theory of Operation of Pressure-Sensitive Gage Fabrication of a Pressure-Sensitive Gage Operation of Pressure-Sensitive Gage VI. FABRICATION OF EPOXY GAGE SECTION . VII. MAGNETIC TAPE RECORDER FOR OCEAN-WAVE GAGES Theory of Operation of Magnetic Tape Recorder . Fabrication of Magnetic Tape Recorder . Calibration and Operation . VIII. MODIFICATION OF STRIP-CHART RECORDER SPEED IX. ANALYSIS OF OCEAN-WAVE GAGE RECORDS Step-Resistance Wave Gages Pressure-Sensitive Gages Tables I II IIl IV Vv VI XI ILLUSTRATIONS Resistance Values in Ohms for 20-Foot Gage for Fresh Water Resistance Values in Ohms for 25-Foot Series Gage . Components for 25-Foot Five-Section Fresh-Water Series-Resistance Gage List of Components for Wave-Gage Holder . . Resistor Values for Salt-Water Parallel Step-Resistance Wave Gage Rul Ass tere eomrcr me ten to: bd acs: 2 peuuls OMY BI ON 841m Jeaddo> peuul) OMY BI ON “y1[09 ‘Ousposod ‘09 Bulseauibug odjluy DJUDS “4a;jNO WOjJ0G ysim (40OY IByOWOJND) jod 4sapjos ash “s9p1os OG /OS Bulsn pjow 481/NG paljyipow ul papjow diy Bulsuas poay 7 "o3e9 FFRIS LOWEM-YSeL] OF YIuN LomMog “6 OINSTY jonba 40 BIUDISISAY JOJOWUId 4Z9d08 jOusydwy SD AN|DA awDS Oo} sNIpy CS-80b21 Uaplag “p409 SJJOA GI| Jawwo1601q OL Japsooay ysnig Japsooay ado, Ad jonba 10 YWdWeW AsO] |OW Jonba 10 OVIId4y G: jonba 40 dW S'IW Aojay AGI Kio L1lOW Pjaijwnig - 12}}0d 4J@-v660¢ H PUD HV YIMS 1SdS jonba 10 YOO!I'0-0'0S-W JAPOW JamodiuydaL c SLIOA 2S-8%7 AlddNS Y3MOd J9VLIOA LNVLSNOD ajqoy a609 JO} S}SOg Buipulg CS-80bZ2| uaplag ‘p405 auIq eulsl deed pasinbas so ‘sissoyy wnuwnyy 31949 O9 S}IOA GII 18 Tork Timer No. 4100 Clock Motor Winding Manual Switch AH&H 20994-BF Clock Switch Line Cord Belden 17408S Amphenol Plugs No. 160-10 Ground green conductor in cable and grounding terminal in amphenol plugs to timer case. Figure 10. Programmer for Wave Gages. Plugs and switch to be mounted in Yight side and bottom of case as mechanically feasible. (Do not mount on lid.) ° Connector Amphenol Connector Type 80MC2M AN 3108B-14S-6S 2 Conductor, No. |8AWG Cable. Length as Desired (6-8 ft.) Figure 11. Signal Input Cable for Strip-Chart Recorder. 19 The metal wave-gage holder is fabricated to the desired length as shown in Figure 12; a list of components used in fabrication is shown in Table IV. Mounting brackets for attaching the holder to the supporting structure should be strong enough to support the holder during severe wave conditions. Figure 13 outlines one type of bracket that has been used in supporting the gage holder on a vertical piling. The gage holder gets two coats of zinc chromate primer and two or three coats of anti-fouling paint as used on ship bottoms. Government agencies may use this paint which is available through Government Services Administration (GSA) supply - Stock No. GS8010-550-8305 for the primer and Stock No. GS8010-290-6651 for the anti-fouling paint. DO NOT PAINT THE GROUND ROD. Install the ground rod after the gage holder has been installed. The holders should be installed so that about 6 to 8 feet are below mean lower low water, 17 to 19 feet out of the water. Only the epoxy wave gage sections that are below or at the water line require anti-fouling paint. Mold release must be removed from the gage sections prior to painting. DO NOT PAINT THE LEAD SENSING TIPS. 3. Operation of a Series-Type, Step-Resistance Wave Gage a. Installation When placing the epoxy wave gage sections in the gage holder, the section having the highest value resistors is the bottom section, and goes into the holder first. The section with the next highest value re- sistors is placed in the holder on top of this section, and so on until the section having the lowest value of resistors is in the top of the gage holder. The power unit, the strip-chart recorder, program clock, magnetic tape recorder (if used) and chart rewinder are connected as shown on Figures 14 and 15. b. Calibration The accuracy of the recorded wave heights will depend directly on the accuracy of the calibration of the gage. There will be enough dif- ference in each wave gage and in each strip-chart recorded to require that each gage be individually calibrated. The ideal calibration would be raising and lowering the gage holder with the gage sections into the water in small increments and marking the strip-chart recorder with each move. Usually, 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 cistern-like basin about 24 inches in diameter with the required depth. A wave gage holder would be a permanent part of the calibration pit. Such 20 a pit should be made of concrete pipe or other nonconducting material; use of a metal wall would cause an inaccurate calibration of the gage. The procedure outlined below has been satisfactorily used for cali- bration of staff-type gages. If feasible, a time of low-wave action should be selected for the calibration. If possible, the sections that are to be removed from the water first are kept inside the steel gage holder. This provides a more accurate gage calibration. If the water is deep enough, place two or three of the sec- tions 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 the succeed- ing sections are below it. When the section having the lowest value of resistors has been removed from the holder (in the desired calibration increments), the other gage sections in the holder should be removed, and a succeeding section should be put in the bottom of the mount, thus all sections having the lowest resistors will be removed from inside the gage holder in succession during the calibration process. Calibration of the gage proceeds as follows: a) If a magnetic tape recorder is used, calibrate it with the strip-chart recorder as outlined in Section VII. b) > Turn thevstrip-chart recorder )!'on-of££!! switch) to, oft": c) Turn the "off-on" power switch on the power supply unit Cop on: d) Remove all epoxy wave gage sections from the metal gage holder. e) Turn on the strip-chart recorder using the switches on the recorder and on the programmer. f) Using the mechanical lever on the recorder penmotor, adjust the recording pen to the left side of the chart paper. g) Place the epoxy gage sections under water being careful to keep the lead tips adjacent to the metal gage holder with about the same spacing from the ground rod as they would have been installed in the gage holder. h) Adjust the calibration resistor on the power unit to provide full-scale reading on the strip-chart recorder. i) Remove all wave gage sections from the water. j) Repeat steps f, g, h, and i until zero and full scale are obtained. Text resumes on page 27 2 TABLE IV LIST OF COMPONENTS FOR WAVE-GAGE HOLDER (FIVE-SECTION, 25-FOOT GAGE) 1. Steel '"'H" Beam 4'' x 4" WF-13 pounds per foot, 25 feet long 1 each 2. Steel rod 1/2" diameter 25 feet long, hot rolled 5 Sear Steelsrod) 3/8unx W/2 25) feet) long, hot rolled Dee NN Ay) Steel z0d73/ 8x 1/2" 10 feet: long, hoty rolled The SUP 5. Steel rod 1/2" x 1/2'! 20 feet long, hot rolled leet 6. Steel plate 3/8" x 6" 20 feet long, hot rolled Lyre Up Steels plate /(2U exe 3n 5) Leet long hot, zolled Te 3 8. Steel bar 1" x 3", 7" long, hot rolled ile 9. Steel bar 1" x 2", 4" long, hot rolled dy 10. Cap screws, type 316 stainless steel, 5/8" x 6" long, Oe 11 threads per inch Hex head 11. Cap screw, type 316 stainless steel, 5/8'' x 1 3/4" long BQ) 1] threads per inch Hex head. i2ee Capescnew,. type Sho sitainiless steely 5/38 x Sol/2" jong 7a 13. Lock washer, type 316 stainless steel for 5/8" bolt 455 i 14. Nuts, type 316 stainless steel, 5/8" regular, 11 threads ANS per inch, Hex head. 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Diagram of Fresh-Water Staff Gage. 25 To Power Supply ( black binding post) No. 14 or 16 AWG Cable between gage site and recording equipment. White To Power Supply (red binding post) White Figure 15. Wiring Diagram for Fresh-water gage section. 26 Ground Rod k) Place all gage sections in water and remove the top gage section from the water 1 foot at a time, and mark the strip-chart accordingly. Continue with the remaining gage sections. 1) Check the strip-chart record for linearity. m) If the chart is not linear, change the voltage out of the d.c. power module to 52 volts. n) Repeat steps g, h, i, j, k, and 1. A change in linearity should be found in the strip-chart recording. If linearity has improved, continue increasing the voltage in small in- crements and repeating steps g, h, i, j, k, and 1 until the desired linearity is obtained. If the linearity is worse, reduce the voltage in small increments and proceed with steps g, h, i, j, k, and 1 until good linearity is obtained. o) Turn off the strip-chart recorder using the switch on the programmer. p) Set the programmer to the desired recording program using screws in the program dial to provide a recording beginning at the selected hour or hours and for the selected number of minutes. q) Place the epoxy gage sections in the metal holder. r) Place magnetic tape recorder in operation. s) Gage is now in operation. c. Maintenance Maintenance of the gage involves changing the paper chart, refilling the ink reservoir, and checking the program units for proper timekeeping. The epoxy gage sections and the metal holder will require cleaning; frequency of cleaning will depend on local conditions. The lead tips on the epoxy sections will possibly grow a covering that looks like a hard powder. This covering will affect the gage accuracy and must be removed; use of sandpaper or steel wool may be re- quired. Reversal of the leads connecting the gage sections to the power supply sometimes changes the rate of covering, and may be tried if desired. Servicing of the recorders and programmers should follow instructions in the manufacturer's manuals. 27 Section III. PARALLEL-TYPE, STEP-RESISTANCE GAGE FOR SALT WATER 1. Theory of Operation of Parallel-type, Step-Resistance Gage Due to the low resistance path created by a film of salt water on the epoxy wave gage sections, the gage design for fresh water cannot be used in the ocean. To compensate for the low-resistance, salt-water film and the increased electrolytic action in salt water, it is necessary to provide low resistance values in the wave staff and to use alternating current and low voltage in the sensing circuit. The circuit in Figure 16 was evolved to permit the use of low-voltage, low-value resistors, and alternating current in the wave-sensing circuit. Analysis of this circuit (Figures 16 and 17) shows that a standard 115-volt, 60-cycle line is con- nected to a constant-voltage transformer. The output of the transformer is a constant 115 volts + 1 percent for powerline variations between 95 and 130 volts. This removes variations in the record that might be caused by a change in line voltage. Output of the constant-voltage transformer is applied to an autotransformer which provides a means for varying the volt- age applied to the wave-gage circuity. This feature of voltage adjustment permits calibrating the wave gage for full-scale indication on the strip- chart recorder. A voltmeter is used to monitor the voltage out of the autotransformer. The selected voltage from the autotransformer is connected to a stepdown transformer which further reduces the line voltage to a value suitable for wave-sensing resistors. The stepdown transformer also isolates the powerline from the wave staff. The secondary winding of the stepdown transformer is connected in series with the variable-resistance circuit provided by the parallel-resistor, water-conducting path, and the primary winding of a step-up transformer. The step-up transformer is identical to the stepdown transformer except that its windings are used in a reverse manner. Output voltage from the step-up transformer is applied to a bridge rectifier and low-pass filter to convert the varying amplitude (caused by changes in water level) of the 60-cycle a.c. source to a d.c. signal suitable for driving the recorder penmotor. The stepdown, step-up trans- former units and the rectifier-filter unit have fixed resistors incorpor- ated in them to aid in getting a linear signal from these units. This circuit utilizing the parallel resistance circuit of the wave staff and the low-voltage windings of the stepdown, step-up transformers is a low-voltage, current-sensitive circuit. Such a circuit must have low resistance electrical connections. It is mandatory that the step-up, stepdown transformers be placed physically close to each other and as near as possible to the wave gage staff sections. Design experience has evolved the resistor values for gages of 20 and 25 feet as listed in Table V. These values operate with the other elec- trical components listed in Table VI, and should provide a gage with good operational features and good linearity. 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BA 24. 26. Zor So 33. 35. 38. 40. 43. 45. 47. 50. Seis 55. 58. 62. 65. For 20-foot gage 3 Ohms 4 6 7 9 0 2 4 6 (0) 2 1 4 6 3 9 6 8 1 8 " Top Section Bottom Section nnn nunfjuon an unjununnn nin wan wn oH wo each each each each each each each each each each each each each each each each each each each each 31 626) by tle Gos Ss Ole @ SW Git SV QaS wimam so S For 25-foot gage .9 Ohms Ww Top Section Bottom Section Cal Un CA Un) alt nb al Ca a a ea al = Ca) Cade Cat Cal) Cal Cal Cad Ur Cal al an al ten each each each each each each each each each each each each each each each each each each each each each each each each each TABLE VI COMPONENTS FOR FIVE-SECTION 25-FOOT PARALLEL RESISTANCE GAGE FOR SALT WATER 1. Programmer, Tork Hourmaster Model 4100 1 ea. 2. Voltage Regulator, Sola Type 20-13-030-1 1 ea. input 95-130 volts, output 118 volts 30 VA. 3. Variable transformer, Superior Electric Co. Model 10B, input ear 120 volts, single phase, 60 cycles output 0-132 volts 2.25 amps. 4, a.c. voltmeter 0-150 volts, Triplett Model 337-S lerear (3) Filament transformer Thordarson No. T21Fll 6.3 volts c.t. 6 amperes. Precision Resistors, wire wound, 1% Type TX-2212, manufactured by Precision Resistor Company, 109 U.S. Highway, Hillside, NJ (O59) Values shown in Table V. 7. Scotchcast Resin #2, Minnesota Mining & Manufacturing Co. 42 lbs. @®) Bar Solder, 50% tin, 50% lead. 6 lbs. 9. Wire solid copper, plastic insulation AWG #14 GS) AE ¥ Resistor, 500 Ohms, 10 watt 1 ea. ‘ é) Selenium rectifier, International Rectifier #Q4B, 130V 4 ea. RMS, 100 MA Capacitors, Sprague 155 P-156P Metallized-paper Tublar 4.0 mfd. 200 volts. AG) Filter choke, Stancor C 1721 1 ea. 8.5 Henrys 200 MA» 14. Box-Mounting receptacle Bendix Scinflex, RB 3102 #10-42214-2P leak Scintilla Division, Bendix Aviation Corp., Sidney, N. Y. 15. Plain Gasket, used with box-mounting receptacle, Bendix 1 ea. Scinflex #10-40450-14 16. Straight plug, Bendix Scinflex RB-3106 #10-42614-2S with 1 ea. #10-40908-141 back shell and #10-40457 Hex coupling nut and #AN-3057-6B cable clamp. 17. Box, aluminum watertight 4 1/2" D x 6 1/2" W x 6 1/2" H 1 ea. Adalet #JP102, A Adalet Mfg. Co. Cleveland, Ohio. 32 40. TABLE VI (continued) Utility box, metal 5" D x 6'' W x 9" H, Black Crackle 2 finish - Bud #CU 1099B. Switch SPST, Arrow Hart §& Hegeman #20994BF 1 Chart rewind, Brush Model #RA-2402-11 il Strip-Chart Recorder Brush Model No. RD-2321-00 (order with 1 following modifications: single channel operation and 50 mm chart width. Old style penmotor #BL 902 and Long Pen #BL 921. Wire solid copper, bare, tinned, AWG #18 50 Cable 2-conductor #20 AWG with 2 high-strength 1 1/6" steel 110 members. Neoprene outer sheath Marsh and Marine Mfg. Co., Houston, Texas, Type #TPSC. 4-conductor #14 AWG rubber covered. Length required to connect wave staff site to recording site. Plug amphenol #160-10 3 Line cord a.c. Belden 17408-S Resistor, 11 Ohms 1% tolerance 10 watts IRC #AS-10 Connector, male cable plug Amphenol type #80-MC2M Connector, female receptacle, Amphenol type #80 PC2F 2 Relay DPDT, 115 volt, 60 cycles Potter Brumfield KRP 11AG 1 Potentiometer 2K-Ohms Mallory M2MPK, or equal 1 Solder, 18 S.W.G. 60% tin/ 40% lead i Socket, Octal, Amphenol #78RS8 1 Connector, female 3-wire polarized type Harvey Hubbell 1 "Twist Lock" #7484. Connector, male base 3-wire polarized type Hubbell #7486 1 Connector, male cap, 3-wire polarized type Hubbell #7485 1 Connector, female base, 3-wire polarized type Hubbell #7487 1 Cable, electrical, rubber covered, three-conductor AWG #18 15 Belden type 8453 Cord - Grip for rubber covered cable 0.500 - 0.625 diameter. 1 aluminum, Pyle-National #DB-10 Cable 2-conductor #18 AWG Belden #8452, or equal 2 NOTE: This list does not include gage mount. 33 ea. ea. ea. ea, ft. fates ea. Pitre The gage will operate in salt-water locations that have little or no change in salinity. If the gage is placed in locations having significant salinity changes, the wave record will vary in accuracy with the changes in salinity. 2. Fabrication of a Parallel Step-Resistance Gage Fabricate the required number of 5-foot epoxy gage sections as outlined in Figure 18. The top gage section will have the lower value resistor connected to the top five sensing plugs, and the resistors will progressively go higher in value until the highest value of resistors are connected to the five sensing plugs, and the resistors will progressively go higher in value until the highest value of resistors are connected to the five sensing plugs on the bottom gage section. The cable from each wave gage section (molded as part of the section) should not extend more than 10 feet from the top of the gage mount. The resistance in the gage cables and leads from the transformer unit connected to the gage cables and leads from the transformer unit connected to the gage cables are part of a low-voltage, current-sensitive circuit. The resistance of these connections must therefore be low; long leads or high resistance con- nections in this circuit must be avoided in order to provide best gage linearity. Wire size in the cables molded into the gage sections should not be smaller than 2-conductor No. 20 AWG in parallel. Fabricate the transformer unit as shown on Figure 19. Wire the transformer unit as shown on Figure 20. Be sure that all connections in this unit are well made and well soldered. This unit may be filled with a clear potting compound available from Dow Corning Company, their No. 182. If this unit is not filled, care should be taken to ensure that it is watertight. Fabricate the voltage control, rectifier-filter unit, and programmer as shown on Figures 10 and 21 and wire as shown on Figures 10 and 22. Strip-chart recorder chart speed may be modified, if desired, as outlined in Section VIII. Fabricate the signal connecting cable for the strip-chart recorder to the desired length using 2-conductor No. 18 AWG cable as shown on Figure 11. Fabricate the metal gage holder to the required length shown in Figure 12. Suitable mounting brackets for the gage holder should meet local installation requirements. Mounting brackets must be strong enough to withstand the forces of wave action expected at the gage site. A bracket design that has been used on vertical piling is shown on Figure 13 which may serve as a guide. Paint the gage holder with two coats of primer and two coats of any good commercial anti-fouling paint. Government agencies may use Government Services Administration GSA Stock No. GS8010-550-8305 and GS8010-290-6651, respectively. DO NOT PAINT THE GROUND ROD. Paint the gage sections that are below and at the water line with three coats of anti-fouling paint. Clean the sections of mold release prior to painting. DO NOT PAINT THE LEAD SENSING TIPS. 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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 40 TRANSFORMER UNIT BD (See Fig. 23) O Z 4 conductor No. 14 or No.I6 — gage cable to recording A O equipment. O Keep these cables in as short = length as practicable. B ES : eon 2 °o ae @ ao i=] oO ag O 3 = O c °o 3 : a = © Cc i O S D O eee O : Epoxy Gage Sections O E O Figure 23. Connecting Diagram for Parallel Step-Resistance Gage Section 4| POWER UNIT PARALLEL WAVE GAGE 115 Volt Line RSs een ais A Name aa Na a aR eR a a ar a a eT: Ia oe =] 1 | 1 | To Transformer Unit | | | | | VARIABLE | I | RECTIFIER UNIT CRANSEGRUIER 1 | | | | | | ! | y | | | | 1 | | | | y | y | | | | | CONSTANT- | PROGRAMMER VOLTAGE TRANSFORMER | | | | | | | | a 4 Conductor Cable Gp To 115 Volt Power Line STRIP-CHART MAGNETIC TAPE RECORDER RECORDER BRUSH MODEL RD-2321-00 ee eae ( Modified) ABCD TRANSFORMER UNIT (Sce Figure 26) CHART REWIND BRUSH MODEL PROGRAMMER Short Cable to Gage RD-2402-1| ( See Figure 23) Figure 24. Hookup Diagram for Parallel-type Step-Resistance Gage. 42 the succeeding sections are below it. When the section having the lowest value of resistors has been removed from the holder (in the desired cali- bration increments), the other gage sections in the holder should be removed and a succeeding section put in the bottom; thus, all sections having the lowest resistors will be removed from inside the gage mount in succession during the calibration process. Calibration of the gage proceeds as follows: a) b) c) d) e) f) g) h) i) JS) k) If a magnetic tape recorder is used, calibrate it with the strip-chart recorder as outlined on page 93. Remove the epoxy gage sections from the gage mount. Set the a.c. voltage-adjust control (autotransformer) on the voltage-control, rectifier-filter, programmer unit to its counterclockwise position. Apply power to the gage system and turn on the strip-chart recorder. Using the mechanical adjusting lever on the strip-chart recorder penmotor, adjust the recording pen to the left side of the recording chart. Place all epoxy gage sections under water. The sections should be placed adjacent to the metal gage holder with the lead contact tips near the ground rod. The spacing between the tips and the ground rod should be nearly the same as that provided when the sections are inside the gage holder. Adjust the a.c. voltage control clockwise to provide full-scale movement of the strip-chart recorder pen. Repeat steps b, e, f, and g until zero and full-scale are stable. Remove the top epoxy gage section from the water 1 foot at a time, and mark the strip-chart recording accordingly. Continue with the remaining gage sections. This is the calibration for the wave gage. If the calibration is nonlinear, clean the lead contact tips on the gage sections, check the electrical con- nections of the epoxy gage cables and the connection to the ground rod, and recalibrate. Mount the transformer unit near the top of the gage holder. Adjust the programmer to provide the desired recording periods of the wave gage. The programmer may be set to provide a re- cording beginning any hour for a selected number of minutes. Hours may be skipped by proper installation of the knurled screws in the programmer dial. 43 1) Place the epoxy gage sections in the gage holder. m) Gage is now in operation. c. Maintenance The gage sections and mount will require cleaning as dictated by local marine growth conditions. Repainting the gage mount and the lower epoxy sections with anti- fouling paint will extend the periods between cleaning. DO NOT PAINT THE GROUND ROD AND THE LEAD TIPS IN THE EPOXY GAGE SECTIONS. Recording charts and ink will require replacement at intervals in proportion to the recording program selected. 44 SECTION IV. RELAY-TYPE STEP-RESISTANCE GAGE FOR SALT AND FRESH WATER 1. Theory of Operation of a Relay-Type Step-Resistance Gage The CERC relay-type step-resistance gage is designed for opera- tion where water salinity is expected to vary widely. This variation may approach that of fresh water or that of sea water with little change in gage operation. This gage holds calibration longer than other staff gages. The gage operates on the principle of water completing a circuit consisting of a power supply, a relay coil, and a switch (the switch is the water path) in series (see Figure 25 on the following page). The gage uses 125 relays for a 25-foot gage, each relay closing when its associated water contact is submerged. Only one power supply is required to operate all the relays. In order that the relays will operate in both fresh and salt water, it is necessary to modify the basic circuit in Figure 25 to the circuit in Figure 26. Electrolytic action in the water path makes it necessary to use alternating current in the gage circuit. However, when an a.c. relay is used, excessive relay chatter shortens relay life. This limitation makes it necessary to select a d.c.-operated relay, and subsequent selection of suitable rectifiers and filters for converting the a.c. gage-circuit potential to d.c. for relay operation. The basic relay circuit requires approximately 18 volts for operation in fresh water. When the same voltage is applied to the gage circuit in salt water, the voltage across the relay coil exceeds the coil voltage rating. To overcome the relay-coil overload, a 28-volt .07 ampere pilot lamp is installed to provide relay protection in salt water. In addition, this lamp will have a lower resistance value when not fully excited, thereby providing a correspondingly higher voltage to the relay coil when used in fresh water. The relays are connected to the copper contacts on the epoxy gage sections so that when the bottom contact on the gage is submerged, relay No. 125 is first to close, and when all contacts are successively submerged, relay No. 1 will be the last to close. The a.c. power-supply voltage to the relay circuit is adjustable by changing a jumper wire on a terminal strip on the power-supply chassis. The voltage should be adjusted to the minimum value that will provide positive relay closure at the location of the gage. For sea water, 9 to 12 volts should be adequate; for most fresh water locations, 18 to 24 volts should be adequate. 45 Relay Water Contact Ground Rod in Water Water Surface Power Figure 25. Simplified diagram of relay-type, step~resistance gage. @ dng arin Silicon Rectifier : 5 INI692 28 Volt — .O7 amp. lamp Relay 1100 ohms 1/2 watt Pull in 5 volts 6MA+ IMA Drop out above 35 ampere turns 6 to 24 V. adjustable Water Contact Gage Ground Rod ~“~s~a_| Water Surface 115 Volt 60 Cycle Figure 26. Modified circuit for relay-type, step-resistance gage. 46 Gage response (relay response) to a rising water surface is prac~ tically instantaneous. Gage response to a falling water surface is directly affected by the water salinity and cleanness of the epoxy gage sections. The epoxy gage sections should be kept as free of sea growth and dirt as local conditions will permit. Visual observations of wave action (counting the number of gage contacts from wave crest to trough) on the staff and comparison with the recorded wave record should provide evidence of proper gage operation. If local conditions permit, cleaning the epoxy gage sections and applying a coat of silicone wax to the epoxy will provide outstanding gage response. (Do not coat the copper contacts.) In addition to the relay-operating circuit, the gage contains the step-resistance recorder circuit which provides the signal to the recorder as dictated by the number of relays activated by the water level. The circuit in Figure 27 shows that when all relays are in the un- energized condition (no gage contacts submerged), the step-resistance circuit is open and no voltage is available to the recorder input. When the bottom gage-contact is submerged and relay No. 125 operates, all re- sistors in the step-resistance network are in series with the d.c. power and recorder input. As each gage contact is submerged and the relays are operated, the resistors are short-circuited. This provides a higher voltage to the recorder as each relay closes (voltage to recorder is higher as the gage is submerged). Thus, the recorder will follow the change in water submergence of the wave staff. 2. Fabrication of a Relay-Operated Step-Resistance Gage Fabricate the required number of 5-foot gage sections as required for the wave station. Table VII is a parts list for a relay-operated gage. Fabrication details of the sections are shown in Figure 28. Resistor values and cable color-code are in Table VIII. Cable lengths for the sections should be selected for the shortest length practicable to reach the location of the relay cabinet. Cost of the 25-conductor cable used in the fabrication of the epoxy sections is about $0.50 per foot, thus, a five-section gage will have a cable cost of $2.50 per foot between the gage mount and the relay cabinet. Fabricate the relay panels and relay power supply according to Figures 29 and 30, and wire them as shown in Figures 31 and 32. Mount these units in the relay cabinet as shown in Figure 33. Modify the strip-chart recorder paper speed (if desired) as outlined on pages Install three female 115-volt receptacles, one toggle switch anda line cord in Tork Timer Model 4100 as outlined on Figure 10. Fabricate a metal gage holder of proper length as shown on Figure 14. Fabricate gage-holder mounting brackets as local installation requirements Text resumes on page 59 47 RECORDER 115 Volts 60 Cycles TIMER 297-94 VOLES D.C. POWER SUPPLY (Regulated) 1500 ohms Resistor No. | Relay No. | Resistor No. 2 : Relay No. 2 : Relay No. 3 : (Controlled by bottom Relay No. 125 gage-contact ) Figure 27. Simplified Diagram for Relay-Gage Resistor No. 124 48 *207eM 3[eS IO yserZ UT asn IOF 93eB OAeM goueystser-deys peyeredo AeToy °*8Z oin3ty 19245 —SSajUlOjS pasinbas so yybua| ‘9jq09 JOyINpUod cz Bnjd 10;9NpUuDD GZ 09 '6yN puo BululW OjosauUIW - 2 ON ysp24yojo0S ulsay Axodg ‘010, b/I 49 it fe de see oe ese ee. fae) | ferme yt tee Nee 12" All holes to clear 6-32 machine screws (No. 28 drill) At SS lo see oe ae wie + See eee |E 7-2": | LAYOUT BASE = 17" —| ALUMINUM ANGLE PANEL MOUNT Note: Panel is astondord 3-1/2"x 19"x 1/8" thick aluminum rack panel. ( Hammertone gray finish) All holes to clear 6-32 machine screws (No. 28 drill) (2 holes) No.33 drill to clear 4-40 machine screws, all others to clear 6-32 machine screws (No.28 drill) PLUG MOUNTING BRACKET Figure 29. 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If the tension is insufficient, it will allow the tape to be pulled through the capstan roller by the take-up reel, resulting in a tape speed too fast for proper recording. If the tape recorder is turned off, the capstan roller must be backed off from resting on the capstan. If the roller is allowed to stand on the capstan with pressure, the rubber roller will indent perma- nently and be rendered useless. Removal of pressure on the capstan is accomplished by placing a pin through the roller bracket into a hole drilled in the front panel. The recorder requires a timer for placing the internal calibration signal on the tape automatically. Figure 47 shows assembly and wiring of this timer. The timer cable plugs into the octal socket on top of the tape-recorder chassis. Calibration of the tape recorder requires a calibration unit which is fabricated according to Figure 48. Parts required are listed in Table XI. 3. Calibration and Operation The wave signal from the gage must have an amplitude that will provide a current of 0.8 milliampere through the magnetic tape head. The voltage level from the wave gage should be greater than 5 volts for the tide capacitor in the tape recorder to have an adequate time constant. The wave signal from the CERC wave gages is more than that required, and the signal level is reduced and adjusted by the potentiometer in the lower center adjusting-port in the front panel of the tape recorder. See Figure 49. The bias frequency to the tape head must be 8.0 milliamperes, and is adjusted by the potentiometer located through the port on the bottom right from center panel position. The internal 4-second period calibration signal also must provide 0.8 milliampere through the magnetic tape head. This signal will be indicated by the left meter on the tape recorder panel. The meter will swing 400-0-400 microamperes when properly adjusted. A centering control on the inside chassis of the recorder is provided to center the calibra- tion signal on this meter. Calibrate the tape recorder by the following steps: a) Turn all controls recessed in the three ports in the bottom center of the recorder panel to their counterclockwise positions. b) Set the centering control on the recorder chassis to its mid- point of rotation. Text resumes on page 98 93 TORK TIMER Model No. 4100 Hourmaster Clock Motor Winding Switch Contacts 4 Conductor No. 18 AWG Belden 8454 - 8 feet long. (or length as desired ) Pin Numbers 2 Amphenol male plug 8 pin octal No. 86CP8 with cap amphenol No. 3-24 Figure 47. Calibration signal timer for magnetic tape recorder. 94 NOTE: Parts mounted on Bud Chassis No. AC- 431 DPDT Switch Amphenol No. 80-PC2F 1500 Ohms Variable Resistor ae Volts D.C. output Mallory M1.5 MPK ACOPIAN CONSTANT VOLTAGE POWER SUPPLY Model I18A05 On and Off Switch Ss To 115 Volts 60 Cycles Figure 48. Diagram of Calibration Unit. 95 TABLE XI PARTS REQUIRED FOR A CALIBRATION UNIT FOR CALIBRATION OF A TAPE RECORDER WITH A STRIP-CHART RECORDER Power Supply Output, 18 volts d.c. at 50 milliamperes input 115 volts, 60 cycle, Acopian Technical Company, 927 Spruce Street, Easton, Pennsylvania, Model H 18A05, or equal. Potentiometer 1,500 Ohms, 4 watt, Mallory M1.5MPK, or equal. Switch DPDT, Arrow Hart & Hegeman #20905 FR, or equal Female receptacle, Amphenol #80-PC2F, or equal Chassis aluminun, 4" x 6" x 3" Bud AC-430, or equal Line cord, Belden, 17408S, or equal Knob Nation Co. HR, or equal Switch SPST, A-H §& H #20994LH, or equal Rubber grommet for line cord 96 1 ea. ea. ea. ea. ea. ea. ea. ea. ea. 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Japsoda4 UaYyM ajoy siyj ul uid Buruipyas aod} gq ( ajou 9as) 2 SS Jaj|OYy uoISUuaL “4 Se a = OUD ag TAL J9}jO UO yaWWOIB Jaqqn4 adD\d uay) / *|884 184j0 UO Bulspag AJ ad0\d *ysuy \ / \ uojsdo5 4jDYS UO jaa1 dD} DIyauBDW ad0}4g \ 7 (UO }aa1 SpjoH) \ / \ \ \ \ 7 -guajo0ju0) 20-08 02S|0M’ loods dne4o1 yjyim pauaysiow Ajjyb1)s ‘Ns umop apis |/np yjojo Buisn yaam yoda adu0 ‘dn ado, yo OP SEMIS poaH edo) 4a}]04 UOISUa} Jaqqn4 UDa|) TaION _— —— SS S55 97 c) Apply power to the recorder, and set the ''calibrate-signal" switch on the front panel to the ''calibrate" position. d) Adjust the right adjusting potentiometer on the front panel to provide a reading of 0.8 volts on the right panel meter. e) Adjust the left potentiometer on the front panel to provide a swing of 400-0-400 on the left meter. If the meter does not swing equally on each side of zero, adjust the centering control on the recorder chassis to obtain equal movement of the meter pointer on each side of center. Due to the inertia of the meter movement, the meter pointer will not provide an accurate indication of the actual current in the meter. To get the precise peak pointer-movement of the meter, it is necessary to stop the synchro shaft at its peak signal point of rotation. To do this, set the switch on the chassis near the synchro to the "calibrate'' position, and grasp the coupling attached to the synchro shaft and turn it manually to provide peak indication on the left panel meter. Adjust the panel control for the proper 400-0-400 movement of the meter corre- sponding to the physical location of the synchro shaft that produces maximum swing of the meter. The centering control may require further adjustment at this time. Adjustment of the caltbration stgnal ts very important as it ts used to standardize the wave gage signal and the spectrum analyzer tn the CERC laboratory. Return the calibrate switch near the synchro to its "operate'' position when the above adjustment is completed. f) Connect the signal cable from the magnetic tape recorder and the signal cable from the strip-chart recorder to the calibra- tion unit as shown on Figure 50. g) Set the voltage-control potentiometer on the top of the cali- bration unit to its counterclockwise position. h) Apply power to the tape recorder and strip-chart recorder, and set the calibrate switch on the front panel to "off". i) Adjust the strip-chart recorder pen to the center line on the recording chart using the manual control on the penmotor. j) Place the tide-capacitor switch on the tape recorder chassis to the "out" position (switch closed). k) Apply power to the calibrate unit, and adjust the strip-chart recorder pen for full-scale indication (one-half of chart width) using the voltage-control potentiometer on the calibration unit. 1) Adjust the bottom center control on the tape recorder panel to 98 To 115 Volt 60 Cycle Power Line To 115 Volt 60 Cycle Power Line MAGNETIC TAPE RECORDER STRIP CHART RECORDER Recorder Pen Motor Signal Cable Magnetic Tape Recorder Signal Cable To II5 Volt 60 Cycle Power Line CALIBRATION UNIT Figure 50. Block Diagram of Calibration hookup. 99 provide an indication of 400 microamperes on the left mag- netic tape recorder meter. m) Move the polarity-reversing switch on the calibrate unit to its other position. The strip-chart recorder pen should indicate full scale on the other side of the chart paper, and the magnetic tape recorder signal meter should indicate 400 microamperes on the opposite side of zero from that found in 1) above. n) Readjust the bias meter signal to 0.8 volt. When switching from "'operate'' to "calibrate", the bias meter will change slightly; this is normal, and will not affect recorder operation. o) The magnetic tape recorder is now calibrated for full-scale recording of the signal that produces full-scale movement of the strip-chart recorder pen. Since the strip-chart recorder pen indicates the maximum wave height produced by the wave gage, the magnetic tape recorder is also so calibrated. Since all strip-chart recorders do not have the same sensitivity, the wave-gage circuitry is adjusted to overcome this deficiency when the wave gage is calibrated. Therefore, the calibration of the magnetic tape recorder must be mated with the calibration of the strip-chart recorder with which it operates. 100 Section VIII. MODIFICATION OF STRIP-CHART RECORDER SPEED The slowest speed of the chart on the recorder as received from the manufacturer is 5 millimeters per second or about 12 inches per minute. To conserve chart paper and lengthen the time between visits to the wave recording station, it is desirable to change the chart speed to a lower value. Three lower chart speeds can be provided for the recorder with fairly simple changes in the gears. These changes will provide a basic chart speed of 2.5 millimeters per second, 1.25 millimeters per second, or 1.0 millimeter per second. Recorder paper comes in rolls 300 feet long on GSA schedule from Judson Bigelow, Inc., 12-12 44th Avenue, Long Island City, New York, Chart No. RA-2911-30 JB. With the recorder operating for 7 minutes each 4 hours and the reduced chart speed of 2.5 millimeters per second, a 300-foot roll will last about 14 days. If different frequency recording periods are desired, the time span for one roll may be calculated. If the recorder is modified to a slower chart speed, wave crests will appear closer together on the chart. A sample of wave periods, using Sine waves, on a recorder chart with speeds of 2.5 millimeters, 1.25 millimeters, and 1.0 millimeter per second are shown on Figures 51, 52, and 53. To modify the recorder chart speed, proceed as follows: a) Fabricate the required gear assemblies and parts for the selected chart speed as shown on Figures 54 through 56. b) Remove the recorder pen. c) Remove the chart platen. d) Remove the chart payout guide and paper tear-off unit. e) Remove the chart driving roller, taking care not to lose the two brass spacers on the ends of the roller. f) Remove the chart speed-shift knob assembly. A thin knife blade “in the side of the main drive-shaft slot will accomplish this. g) Remove the snap spring on the main drive shaft. Observe the spacing between the spring and the recorder frame, and retain this distance when recorder is re-assembled. 101 a potter PEP NETH AE HELE ATA =F =r H ==22 225205 aay nee Bisa ae Bees: Pa eee oe, Be See SS S05 Se eae ta rae ee = eee = oe reat iS Siesta = Sect Sree eet a A Sa aes Segue = = ieoteiaaeet ISS SEs —— : cele Gea pp eS SEES SB e2ee Sees 2S 255 = ae VORA === SS = = = = == Se ee ee ee 5-Second Wave Period —= JALAL AE LER? qe pee iecee = a - EARN SSS S==25=== =n (WAN a = SZEz==ar==s= 3 See eee sSSSS=e) ===== SS Sees sec eee == = eee 20-Second Wave Period Figure 51. Wave records with chart speed of 2.5 millimeters per second 102 = oa = Fee Reece i a = 2 G2 225s eee ee SE SSS =" — eoeeeeee pf - sesso uae === aS Se aa eyes esas Wy NPN 20-Second Wave ay Figure 52. Wave records with chart speed of 1.25 millimeter per second. 103 HF H+} H i] ry H 7] + revel Biz H = i] EHH PAH iZ: EE RH S2S5 EH S == tt Si = {tt HOARE AEA A = HISTO srnesi 10-Second Wave Period f= aS SS Sea one ar HES TEES USS eases: Hg ga! 2 Bars save San 2222222 i : Bee eee eee S=i/===r = Sap Pease eae Seco eet ee = = = Se == = ==" Ste: = Ss ‘ SS SSeS SS 20-Second Wave Period Figure 53. 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The gear train should run freely when it is properly adjusted. Lubricate the shafts and gear trains when reassembling. The re- corder gear assembly before and after modification is shown on Figures 57 and 58. 108 “UOTIEOTFTpow 02 JOTId Tapxoser ysnzq utTea. IeAE5 "2 9an3sTty ~ ~ res m & ® 109 “UOTIVITFTPOW I9IFe LopLOeL ysnzq utTer} 41e9ey *gg oANSTYy A\quiassy 1089 man 110 A\quiassy 1Da9 map Ie Section IX. ANALYSIS OF OCEAN WAVE GAGE RECORDS Step-Resistance Wave Gages Strip-chart recordings taken at CERC ocean wave recording sta- tions are analyzed for significant wave height, Hs, and significant wave period, Ts. The visual method used in analyzing strip-chart recordings (as opposed to automatic magnetic tape analysis) for a significant wave height and wave period follows: a) b) c) d) e) From a chart run (normally 7 minutes), select as nearly as possible the minute with a wave train which contains most of the highest and most uniform waves. Determine the period of the wave selected in step a) by using the wave-period template according to instructions (Figure 59). When the wave period on the chart falls between two of the periods shown on the template, the analyst may approximate what he considers will be nearest to the exact period. For example, if the period is about halfway between the 5-second template and the 6-second template, then the period is about 5.5 seconds. Use the listing below to determine which wave should be measured to get the approximate significant height of the waves. The wave-height template will aid in determining which wave is to be measured for height. Wave period (seconds) Wave to measure 3 3rd highest SES 3rd highest 4 2nd highest 5 2nd highest 6 2nd highest 7 2nd highest 8 or longer Ist highest With the proper wave-height template (Figures 60 and 61), determine the height of the wave given by step c) by finding the rectangle on the template whose top line comes nearest to to the crest when the bottom line is on the preceding trough. The wave height, in feet, is indicated by the number on the rectangle. Records with wave heights less than 1/2-foot are listed on the compilation sheet (Figure 62) as calm - without listing the wave height. However, the significant wave period for such records is determined and is indicated on the compilation sheet. aynuiw jad Sayou! 9 (:928209e IvaTD WorZ oQeoTIqGes) 93eTdway potzed-oAem oTdues "6S oin3ty ajO|dwa} ayy yo Jaqunu ayy Aq payooipul s¢ }4_+__+__+_+ +4 c¢ si'spuodas ul 'SaA0M au} 40 polsad ayy *3)0|dwa} 0 UO Saul] [091,49 AAIINIaSUOD ujIM uBbI|D 4J0Yyd D UO UMOYS SD S2ADM yO Synod} JO $4yS9a19 BAIINDaSUOD UAYM 40 ds Japsoda1 10 l | JO paads Japsooas 104 ¢ ¢ asp 2 Figure 60. Sample of wave-height template (Fabricate from clear acetate using proper gage calibration.) 113 4 Figure 61. Sample of wave-height template (Fabricate from clear acetate using proper gage calibration.) 114 Location Gauge Recorder ATLANTIC CITY N J STAFF BRUSH TIME TIME DATE OF PERIOD HEIGHT DATE OF PERIOD HEIGHT 1965 START (SECONDS ) ( FEET ) (SECONDS ) (FEET ) S20 | 772 ON | 1g Os | cn Eero ee | me | NG | Reo ee ee Biever wal eee odo wa CO (Ea 6.0 GOO MEa ERTS 0) SRE CNU aaa | Q (Rood as IES SN. Se ee 320 |, Reps Cort cae ae eel ae aloo meee ea aoe Pe age a B 0 [0800 | no Goon |pEn sktppHD An cogma! Mts soem! Paryoe ina Tao Bae (cs a eS ee ooo | 0 0 Gio ceed MO Boa Ce ME Gear ee PAciafoh as a ee A ee Peery an es) (erolcTo a RE er i ae Re aA ae Er ae (Cts ihn a a aie (ite aes (oy Tina ani a -—6.0 — Gore Ey ome CE Ee 6.0 [eo se (a a eta sce ES [(ave°ooiez Saal ata ae Ce re) Petes ger al dco Me Maa ioe Racine pyar ore Pee eames) igyootce lee Ee ee yeas 2.0 [512° er Leas Tao a sot PEG 2.0 tS een ea) 0 25 (dS Ve eee See a iio Le Sire ee eel OQ a casee, 000 BigIe feu dledes eel 9.0 ie? 0 (at 11/350! GLOmbeae | SEES 7 Gi Melange eT Ss 6,0 265. ith SS DES ie en 6.0 0 Brig@a"0 il ae (oS (ee Big een Ea vehi Lia ie es a7 ae | NS Wy (icons a es a ame yon ad (G)1CoYo ee a SE | ee ( (Ee eyo een ae eXiiin REinne EE ERE ee | iin an ee loon | Bo mel BEB-100 Figure 62. Wave-data compilation sheet. IS 2. Pressure-Sensitive Gages Due to the depth-period attenuation present when wave record- ings are taken using a pressure sensor placed near the ocean bottom, the recordings will require a correction factor to obtain a true wave- height reading. To obtain the true wave-height data (significant height and sig- nificant period), use the following procedure: a) Determine the significant height and period outlined in the in the method for step-resistance gages. b) Using the significant period refer to Figure 63 and find the line representing this wave period. c) Determine the water depth at the time the recording was taken. d) Intersect the water depth and wave period on the period curve. e) Read the K (response) factor below the point of intersection. f) Divide the significant height (found in a) above) by the K factor to obtain a corrected wave height. The curves apply only to a wave gage mounted on the ocean bottom. If the gage is mounted near the surface, additional curves will be required. Data for preparing these curves (K factor) is available on page D2 and Tables D-1 and D-2 of CERC Technical Report No. 4, "Shore Protection. Planning and Design", 3rd Edition, 1966. 116 *spotied ovem pue syjdep snotaea oJ seAand asuodsez ainssertg ‘*¢9 oan3ty wo}jog uo Buljsay abp9 104 404904 esuodsay a4 nsseid)) y TOuE Copaepaae ary sr eetartea Hf G x jyBiay ||DWS yO SAADM |DPIOYI04) 40} 1D payndwiod san|DA :ajON PAL A 0) 2 8 $994 Ul yJdaq Woj}jog 117 Tee i Sted an wee mite % ai ory OF ig, Samia UNCLASS IF [ED Security Classification DOCUMENT CONTROL DATA-R&D (Security classification of title, body of abstract and indexing annotation must be entered when the overall report is classilied 1. ORIGINATING ACTIVITY (Corporate author) 2a. REPORT SECURITY CLASSIFICATION Coastal Engineering Research Center (CERC) UNCLASS IFIED Corps of Engineers, Department of the Army Washington, D. C. 20016 3. REPORT TITLE CERC WAVE GAGES 4. DESCRIPTIVE NOTES (Type of report and inclusive dates) 5- AUTHOR(S) (Firat name, middle initial, last name) Leo C. Williams 6. REPORT DATE 7a. TOTAL NO. CF PAGES 7b. NO. OF REFS December 1969 124 0 8a. CONTRACT OR GRANT NO. 9a. CRIGINATOR'S REPORT NUMBER(S) b. PROJECT NO. Technical Report No. 30 9b. OTHER REPORT NO(S) (Any other numbers thet msy be aesigned this report) 10. DISTRIBUTION STATEMENT This document has been approved for public release and sale; its distribution is unlimited. 11. SUPPLEMENTARY NOTES 12. SPONSORING MILITARY ACTIVITY CERC has used wave gages to gather prototype wave data since 1948. Two basic types of gages are now used in the field - the step-resistance staff gage and the underwater pressure-sensitive gage. CERC has developed three types of step-resistance staff gages - a series type for use in fresh water, a parallel type for use in salt water, and a relay-operated type for use in either fresh or salt water or in water where wide changes in salinity occur. The pressure gage can be used in water of any salinity. The series and parallel gages have an accuracy of +5 percent plus the spacing of one sensor increment. The relay gage has an accuracy of +2 percent plus the spacing of one sensor increment. The accuracy of the pressure-sensitive gage is not as precise as that of the step-resistance gages. The report describes each gage and the theory of operation, details of fabrication, steps for calibration and installation, and requirements of maintenance. DD 2%"..1473 Secoctre Pon smu usc. en? UNCLASSIFIED curity Classification UNCLASSIFIED Security Classification KEY WORDS Ocean-wave gages Oceanographic instrumentation Step-resistance wave gages Strip-chart wave records Magnetic tape wave records Wave-record analyzer (magnetic tape) UNCLASSIFIED Security Classification *squawatinbar a.ueucjUTeU pue UOTIET[eISUT puke UOTJeIqTTed TOF sdajs ‘uoTJeITIGey Fo s{tejep ‘uotjetedo fo Aroayi ay. pue a8e3 yoea saqtiosap qsodezr oy, ‘*sasdeB adueystsaq-daqys ay} se azeinooe se you st ‘AqLUTTes Aue FO 193eM uT pasn ‘a83e8 aanssoid ayy, -imd90 ATUTTeS UT SadueYyD opm eraYyM Idem UT IO 19}eM QYTeS IO YSeTF T9yRIA ut osn 10F odkz poyerado -AeTol e pue ‘ra}2emM 2Tes LToF odXq [oTTered e ‘1a}zeM YSoLF I0F adky soties e - sases xyes Jo sadkz va1y podopfanep sey DyYq) ‘ade3 SATIISUaS-9Insseid Ia,eEMIepuN 93Yy} pue 33e3B FyeYS aDueYSTSer-days dy. - P[etF sy} UT pasn mou are saded Fo saddky DIseq OM] ‘8H6T aduts e.ep anem adkj0JoI1d Leyes 02 sades aaem pasn sey DYqD “O °T “swetTTtM IT (aIAdISSVIONN = OF “ON WNGNVYOWEW IVOINHDSL eTItL I IazXk[eue ploset-oneM *9 spiosei1 odej-otjauseW “Ss spiodei yaeyo-dt4135 ‘py soses aduejstser-daqs “¢ uoT}eJUSUMI4SUT otydeisouerssg * so3e3 oAeM-Ub3aDQ “T “soTqei [TI pue suorzeIySN{Tt ¢9 Burpntout ‘dd ~Z~ 6961 requiaceq SWETTTIM “D9 O8T Aq SHOVD AAVM DUA 91002 °9 “a ‘uczBuTysem 49 ‘YALNAD HOUVASTY OYDNA TVLSVOD AW “Ss “f N *sqjuomertnbar a.ueusjUTeU pue UOTIL[[eVISUT pue UOTJeIqT[Ted TOF sdays ‘uOTJeITIQeF FO S[Ie.Op ‘uotzeredo Fo ALOay 9Yyi pue ade3 yoea saqtaosep yxoder ayy, -sose3 aouejstsei-daqys ay. se aqeainose se you st ‘AzLUTTeS Aue Fo 197eM ur pasn ‘a8e3 oinssaid ayy, -ind90 AZTUT[eS UT sodueYyo aptM azraym Ia}eM UT IO 19}eM ATES LO YSaTF IayITS ut asn 1oF adkz payeszedo -ke[ai e pue ‘iajiem yTes IoF odkq TaTTeired e ‘1a2emM ysoaz A0F Odky saties e - sased xyes Fo sadkz aary. podofansp sey DyqD ‘o3ed @ATITSUaS-9insseid Ia}eMIepuN 3yz pue a8e3 Fyeys ooUeYSTSoI-doqs ay. - PIetF ay. 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