Installation manual

SimradES70
Aboutoutputpower
Theechosounder’stransducerconvertstheelectricalinputpowertoasoundtransmitted
intothewater.InthemajorityofthetransducersmanufacturedbySimradthe
transducer’spowerefciencyisbetween50and75%.Thismeansthatbetween50and
75%oftheinputpoweristransmittedassound.Transducersfromothermanufacturers
mayhaveaslowas5%powerefciency.Naturally,itisveryimportantthatyoucheck
thisparameterwhenyouwishtopurchaseatransducer.
Theechosounder’soutputpowerisameasurementonhowmuchelectricalenergy
theampliercansenddowntothetransducer.Themaximumpowerislimitedby
thetransduceryouhave,andhowmuchpoweritmayacceptfromthetransmitterfor
conversiontoacousticenergy.Ifyousendtoomuchpowerintothetransducer,youmay
inictpermanentandunrepairabledamage.
Thesourcelevel(SL)isameasurementonhowmuchacousticenergythatisinfactsent
outbythetransducer,howhigh“volume”itwillemit.Thesourcelevelismeasuredas
“soundpressure”onemeterbelowthetransducerface,anditisgivenidBre.1µPaat
1m.
Inordertoknowhowmuchpoweryoucanuseyoumustknowwhatkindoftransducer
youareusing.ProvidedthattheechosounderhasbeeninstalledwithaSimrad
transducer,andyouknowwhattypeitis,thisisnoproblem.Allnecessaryparameters
aboutthetransducerarethenknownbytheechosounder,andthesoftwareinthesounder
willensurethatyoudonotoutputtoomuchpower.Ifyouuseathirdpartytransducer
youmustmanuallycheckthattheoutputpowerfromtheSimradES70doesnotexceed
thepowerrating.
Note
Ifyousendtoomuchpowerintothetransduceritwill–justlikealoudspeaker–be
damagedbeyondrepair .
Ifthetransducerreceivestoomuchpowerfromtheechosounder,itwillalsocavitate.
Thisisaphysicalphenomenoncausingtheappearanceofgasbubblesimmediately
belowthetransducerface.Whenthishappenshardlyanyenergyissentintothewater,
andthetransducerfaceissubjecttophysicaldamage.Thecavitationdependsonthe
powerapplied,thephysicalsizeofthetransducerface,howdeepthetransduceris
mounted,andtheamountofcontamination(airandparticles)underthetransducerface.
Transducerswithalargefacecanacceptmorepower.
Nearsealevel,minutebubblesofmicronorsubmicronsizearealwayspresentin
theocean.Whentherarefactiontensionphaseofanacousticwaveisgreatenough,
themediumrupturesor"cavitates".Forsoundsourcesneartheseasurface,the
ever-presentcavitationnucleipermitrupturetooccuratpressureswingsoftheorder
of1atm(0.1MPa),dependingonthefrequency,duration,andrepetitionrateofthe
soundpulse.CavitationbubblesmayalsobeproducedbyBernoullipressuredrops
associatedwiththetipsofhigh-speedunderwaterpropellers.Naturalcavitation
iscreatedbyphotosynthesis.
112
343539/B