Installation manual
Wheretomountthetransducer
WHERETOMOUNTTHETRANSDUCER
Asingleanswertothequestionwheretolocatethetransducer
cannotbegiven.Itdependsverymuchonthevessel’s
construction,howthehullisshapedandhowthewaterruns
alongthehull.Therearehoweveranumberofimportantguide
lines,andsomeoftheseareevenconicting.
Mountthetransducerdeep
Mountthetransduceratadeeppositiononthehull.Considerthe
situationswhenthevesselisunloaded,andwhenitispitching
inheavyseas.
Thereareseveralreasonsforthis.
1Theupperwaterlayersoftheseacontainamyriadofsmall
airbubblescreatedbythebreakingwaves.Inheavyseasthe
upper5to10metresmaybelledwithair,andthehighest
concentrationswillbenearthesurface.Airbubblesabsorb
andreectthesoundenergy,andtheymayinworstcases
blockthesoundtransmissionaltogether.
2Anotherreasontogodeepisthecavitationinfrontof
highpowertransducers.Cavitationistheformationof
smallbubblesinthewaterduetotheresultinglocal
pressurebecomingnegativeduringpartsoftheacoustic
pressurecycles.Thecavitationthresholdincreaseswiththe
hydrostaticpressure.
3Thetransducermustneverbeliftedfreeofthewatersurface.
Transmittingintoopenairmaydamagethetransducer
beyondrepair.Mountingthetransduceratadeepposition
onthehullpreventsthis.
4Ifthetransducerisliftedupfromthewaterduringheavy
seas,itmaybedamagedwhenthehullstrikesbackatthe
seasurface.Thisisespeciallyimportantforlowfrequency
transducerswithlargefaces.
Mountthetransducerawayfromprotruding
objectsonthehull
Objectsprotrudingfromthehull,suchaszincanodes,sonar
transducersoreventhevessel’skeel,generateturbulenceand
ownoise.Holesandpipeoutletsarealsoimportantnoise
sources.Theymayactasresonantcavitiesamplifyingtheow
noiseatcertainfrequencies.Donotplaceanechosounder
transducerinthevicinityofsuchobjects,andespeciallynot
closebehindthem.Forthesamereason,itisveryimportant
thatthehullareaaroundthetransducerfaceisassmoothand
levelaspossible.Eventracesofsealingcompound,sharpedges,
protrudingboltsorboltholeswithoutllingcompoundwill
createnoise.
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