ECHO SOUNDER Objectives: 1. Describe Describe basic basic princi principle ple of of marine marine echo echo sounin sounin! ! e"uipmen e"uipmentt #. $entif% $entif% the main main component components s on a simple bloc& bloc& ia!ram ia!ram ' state state the function of each (. State the the ph%sical ph%sical factors factors )hich a*ect a*ect the velocit% velocit% of soun in )ater )ater +. Operate a t%pical echo souner ' emonstrate basic user maintenance ,. Distin!ui Distin!uish sh bet)een bet)een ran!e ran!e an phase phase an emon emonstra strate te a)are a)areness ness of suin! )ron! phase -. Distin!ui Distin!uish sh bet)een inaccurac inaccuracies ies cause b% instrument instrument scale error error ' those cause b% false echoes. /. E0plain E0plain causes causes of inaccuracies inaccuracies ue to instrume instrument nt or scale error error an state state their their li&el% li&el% ma!ni ma!nitu tue e an measure measure that that ma% ma% be ta&en ta&en to eliminate them . Reco! eco!ni ni2e 2e vari variou ous s t%pe t%pes s of fals false e echo echo that that ma% be recor ecore e escribe their formation an states the possible action to remove them from trace 3. Desc Descri ribe be the the pote potent ntia iall err errors ors ue ue to trim trim heel heel an an tran trans suc ucer er separation.
$n orer to navi!ate safel% one of the prime concern is to &no) the epth belo belo) ) the the ship. ip. 4n echo echo soun soune err is esi esi! !ne ne to pro provi vie relia eliab ble information on epth belo) a ship to ai navi!ation particularl% in shallo) )ater. )ater. Some times it is also refere refere as echo sounin! e"uipment. Soun Soun navi!ation navi!ation an ran!in! ran!in! SON4R is an acron%m acron%m )hich refers refers to s%stems s%stems that use trasmission an reception of acosutic ener!% in )ater. 5his is a ver% ver% )ie )ie term term )hic )hich h incl inclu ues es all all moe moerrn s% s%st stem ems s that that prop propa! a!at ate e acoustic or electroma!netic ener!% into sea)ater to etermine vessel6s spee or epth of )ater uner &eel. 5he echo souner uses soun propa!ation techni"ue to measure measure the epth epth belo) the ship. ship. Soun Soun ener!% ener!% 7also 7also calle calle acoust acoustic ic ener!%8 ener!%8 is transmitte verticall% o)n from the ship an re9ecte bac& as echo after stri&in! the seabe. 5he time ta&en for the return of echo is measure an this provies the epth of )ater as per ajacent e"uation.
5he echo souners are !en !eneral erall% l% es esi!n i!ne to operate an recor epths assumin! the spee of soun in )ater as 1, m;s. 5his value is ta& ta&en for for calc calcul ulat atio ion n purpose. 5he velocit% of soun in )ater can var% 1++ 1+ +, m;s to 1, 1,(, (, m;s an an ma% be a*ec a*ecte te b% atm atmosph ospher eric ic con conit itio ions ns li& li&e temp temper erat atur ure e pressure salinit%. salinit%. 5he transmission transmission of acoustic ener!% for the purpose of epth sounin! can be in the form of continuous )aves or in the form of short an rapi pulses. 5he latter is preferre an majorit% of echo souners use this this s%stem of short an rapi pulse. One of the peculiarit% of this s%stem is that acoustic pulses are transmitte an receive b% a sin!le transucer )hereas continuous )ave s%stem re"uires one transucer to transmit an another to receive.
PARTS OF ECHO SOUNDER 1. Disp Displa la% % Unit Unit:: 5his 5his is loca locate te on the the navi navi!a !ati tion onal al bri!e. 5he ispla% unit can be a paper recorin! t%pe or i!ital ispla% t%pe.
enerato >enerator: r: 5his prouce prouces s electr electrica icall pulses pulses )hich are sen to 5ransucer 5ransucer.. 5he pulse !enerator can be inte!rate into ispla% unit or completel% separate epenin! upon manufacturer. (. 5ransucer ransucer:: 5his is locate locate at the bottom bottom of ship in a tan& &no)n &no)n as as trans transuce ucerr compar compartm tment ent.. 5he trans transuce ucerr conver converts ts electr electrica icall pulses into soun ener!% 7acoustic ener!%8 at a fre"uenc% of 1# ?H2 to # ?H2. 4n internal cloc& starts at this time. 5hese pulses are irecte to)ars the sea be )ith the help of transucer an )hen pulses are are re9ec e9ecte te bac& bac& from from seab seabe e the the tran trans suc ucer er conv conver erts ts the the re9ecte soun )aves into electrical pulses.
Some lar!er vessels ma% be @tte @tte )ith )ith multiple trans transuce ucers. rs. 5his 5his is "uite important )hen )hen navi!a navi!atin tin! ! in areas of limite epth. +. 4mpli@er: 5he electrical si!nals receive from transucer are pass passe e thro throu! u!h h an ampli@er to increase the stren!th of receive si!nal. 5he internal internal cloc& notes the time )hen pulse is returne an so the time ta&en is measure.
CONTROLS OF ECHO SOUNDER 5here are man% controls to ajust the performance performance of the e"uipment an to operate it at various epths. 5he controls ma% var% epenin! upon the manufacture manufacture but the !eneral controls are as follo)s:
1.Ran!e S)itch A to select the ran!e bet)een )hich the epth is be chec&e chec&e e.!. e.!. B , , m m 1 A 1 1 m m 1 1 A # m etc. 4l)a%s 4l)a%s ch chec& ec& the lo)est ran!e @rst before shiftin! to a hi!her ran!e. #.Un #.Unit it sele select ctor or s)it s)itch ch A to sele select ct the the unit unit feet feet fath fathom oms s or mete meterr as re"uire. (.>ain s)itch A to ajust the sensitivit% sensitivit% of the e"uipment. e"uipment. 5his is ajuste such that the clearest echo line is recore. Care shoul be ta&en not to set it too hi!h or too lo). 4 settin! )ith spec&le bac&!roun is consiere satisfactor%. 5oo hi!h a !ain )ill blac&en the ispla% an too lo) !ain ma% not return enou!h echoes.
+. 4uto: to ajust the ran!e scale an clutter level accorin! to epth. $n auto moe !ain is ajuste automaticall%. ,.=aper spee control A to select the spee of the paper A usuall% t)o spees available. -.er -. ero o 4 4jus justm tment ent or Drau! Drau!ht ht settin settin! ! contr control ol A the echo echo soune sounerr )ill )ill normall% normall% ispla% ispla% the epth epth belo) the &eel. &eel. 5his s)itch s)itch can be use to fee the ship6s rau!ht such that the echo souner )ill ispla% the total sea epth. 5his s)itch is also use to ajust the start start of the transmission transmission of the soun pulse to be in line )ith the 2ero of the scale in use. /.i0 /.i0 or event mar&er mar&er B this button is use to ra) a line on the the paper as a mar& mar& to inicate certain time e.!. passin! passin! a navi!ation navi!ational al mar& )hen a position is plotte on the chart etc. .5ransucer chan!eover s)itch A in case vessel has more than one s)itch e.!. for)ar an aft transucer. 3.Dimmer A to illuminate the ispla% as re"uire. RANGING $n echo echo soun ouner er the st% st%lus lus rotat tates )ith ith con constan stantt sp spe ee an the the transmission ta&es place )hen st%lus passes the 2ero mar&. hen hi!her ran!e scale is selecte the transmission )ill ta&e place )hen the st%lus comes to 2ero but the st%lus spee is reuce because st%lus has to remain emain on the the pape paperr for for lon! lon!er er peri perio o of time time sinc since e the the echo echoes es are are returnin! returnin! from !reater epth. 5his s%stem is &no)n as ran!in!. 5he t%pical ran!e scales are provie as B, m B1 m B# m B( m B +m an so on.
Since the same len!th of paper no) covers a lar!er epth the !rauations become closer an it becomes iFcult to rea epth accuratel%. =hasin! arran!ement arran!ement is use to avoi this. Ran!in! is techni"ue )ere the scale of the echo souner is &ept constant an the st%lus is varie accorin! to the epth scale chose. E.!.B B1 B # B( mtrs an so on PHASING 5he spee of st%lus is &ept constant in phasin! arran!ement. Ho)ever the transmission point is avance. =hasin! is a metho use in echo souner to etermine epth of the sea bottom. $n this metho the spee of the st%lus is &ept
constant an the ran!e scale is chan!e from B1 mtrs 1B# mtrs #B ( mtrs an so on.$t is important that the echo souner ran!e chan!e an re!ularl% chec&e.
ERRORS IN ECHO SOUNDER $t is ver% essential to &no) the errors an limitations of echo souner )hile usin! for intene purpose. 5R4NS<$SS$ON 5R4NS<$SS$ON G$NE ERROR asic )or&in! of Echo souner e0plainin! st%lus ' pen arm $t is essential to ensure that pen arm is reference at 2ero mar& of the scale intene for use. $f this is i s not correctl% set an aitional error &no)n as transmission line error coul occur.
S=EED ERROR 5he spee of soun )aves is assume to be constant at 1, m;s for calculation purpose. Ho)ever this spee varies )ith chan!es in i n atmospheric pressure temperature an salinit% of )ater. )ater. $n such cases the the e"uipment )ill not be able to provie accurate accurate measurement. >enerall% an increase increase in temperature salinit% or pressure )ill result in an increase in spee an the epth inicate )ill be less than the actual epth. 5he value of spee of soun )aves )aves throu!h )ater as 1, m;s is an international stanar an provies an acceptable e!ree of accurac% for most commercial shippin! re"uirements. Ho)ever if it becomes necessar% to appl% corrections 4miralt% table N=1(3 provies @ne corrections. $n Re sea )here salinit% an temperature of the sea)ater are hi!her the epth inicate b% an echo souner ma% be about , I less than the actual epth. 5he spee of soun in )ater epens upon the ensit% of )ater. )ater. 5he spee of soun )aves is lesser in fresh )ater than in sea )ater ue to the i*erence in in ensities. 5his means that soun )aves )ill ta&e more time to to travel in )ater of lesser ensit% 7e! resh resh ater8 ater8 than in )ater of !reater ensit% 7 e! Salt )ater or Sea )ater8. 5he ensit% of )ater epens upon temperature salinit% an atmospheric atmospheric pressure.
Hence it is "uite essential to e0ercise e0ercise precautions )here atmospheric conitions are abnormal.
SECOND TRANSMISSION ERROR hen echo souner is use in
EFFECT OF SQUAT $f a vessel is e0periencin! s"uat the recore epth )ill still be the epth uner transucer irrespective irrespective of the s"uat. 5his can be "uite critical )hen s"uat is in e0cess sa% #. m or more. 5he eep rafte vessels or an% other vessels )hich are concerne )ith U?C ma% re"uire epths fore an aft. Hence aitional transucers are @tte to inicate the epths from for)ar to aft. CHART COMPARISION- INDICATED DEPTH
Siti Sitin! n! of tran trans suc ucer er is ver% ver% impo import rtan ant. t. 4 @0e @0e cor correcti ection on ma% be applicable if the transucer is not situate at the lo)est level of &eel. Similarl% e0cessive trim or list ma% a*ect the overall U?C. DOUBLE ECHOES 4 ouble echo is cause )hen transmitte pulses after re9ection from sea bottom are a!ain re9ecte from the )ater surface or ship6s hull. 5he secon echo is never as stron! as the the @rs @rstt echo echo.. 5he 5he echo echo souner )ill sho) t)o la%ers of echo on the ispla%. 5he )ea&er one is usuall% the ouble echo. 4 chan!e in the selecte epth scale or sensitivit sensitivit% % control control can remove remove this error. MULTIPLE ECHOES
5his is similar to ouble ouble echo but re9ection re9ection bet)een the seabe an an ship6s hull ta&es place several number of times. 5his usuall% occurs in lar!er epths usuall% !reater than 1 meters. 5his ma% cause several echoes
to be recore an ajustment of the sensitivit% control selecte epth or scale coul provie a better inication of true epth. ECHOES FROM OTHER OBJECTS IN SEA WATER WATER Some sea objects li&e sea)ee shoals of @sh or plan&ton ma% sometime re!ister stron! echoes. $n such case use alternate means to cross chec& the epth. One of the metho is to ouble chec& the position of ship an verif% the epth from navi!ational chart. TURBULENCE AND AREA AREATION TION hen soun )aves are re9ecte i*usel% ue to air poc&ets or bubbles it a*ects the capabilit% of echo souner. Here aeration refers air bubbles )hich pass close to the transucer )hich )ill re9ect an i*use the transmitte ener!%. ener!%. 5he air poc&ets or bubbles are cause b% turbulence in rou!h )eather cross currents or eies. 5u 5urbulence is also cause )hen ship moves astern on en!ine thus capabilit% of echo souner is a*ecte )hile movin! astern. PYTHAGORAS ERRORS 5his error is cause cause )hen transmitter is locate from the receiver. $n moern e"uipment the i*erence in the len!th throu!h )hich the acoustic pulses have to travel tr avel is accounte for fo r.
a)a%
INTERFERENCE FROM OTHER ECHO SOUNDERS $n hi!h traFc ensit% areas it ma% happen that pulses transmitte b% echo souner of one ship are receive b% the echo souner of another ship. 5here is complete bloc&a!e of the ispla% unit. 4n ajustment of !rain control can eliminate e liminate this error. error. TRANSDUCER LOCATION 5he location of transucer is important concern in proper functionin! of echo soune sounerr. Obviou Obviousl% sl% transu transucer cer shoul shoul be locate locate a)a% a)a% from from areas areas close close to source of noise. 5he main problem encountere is stream of air bubbles ue aerat aeration ion.. Henc Hence e trans transu uce cerr sh shou oul l be site site in su such ch a plac place e )her )here e e*ec e*ectt of aeration is minimum on oesn6t e0ist. 5here is al)a%s turbulence aroun the bo) or stern of the ship. o) )aves !enerall% create stream of bubbles on aroun "uarter len!th of ship from for)ar. 5he e0act location of bo) )aves epen upon shape of bo) spee an raft of ship.
5he best place to install a transucer is )here there is least possibilit% of aeratio aeration n in )ater )ater uner uner the ship an minimu minimum m interfe interfere rence nce from from en!ine en!ine or propeller vibration.