Installation manual

Basictheory
BASICTHEORY
Thischapterexplainssomeofthebasictheoryrelatedtosettings,
errorsourcesandnoiseconditions.
Settings
Asonarwilltransmitasoundwaveintothewateraroundthe
vessel.Whenthissoundwavehitssh,bottom,orotherobjects
inthewater,apartofthesoundwillbereturnedasechoes.
Theseechoesarecollectedbythesonar,interpretedbythesonar
computers,andpresentedonthedisplay.
Themostimportantinterpretationishoweverlefttoyou,and
itmayoftenbedifculttodistinguishtheechoesandidentify
targets.Inordertohelpyouwiththis,theSH90sonarprovides
numerousadvancedlterandgainfunctions.Youcanalsotilt
thesonarbeamverticallyinordertoachieveanoptimumresult,
andyoucanusetheverticalslicetoview“across”intothewater.
Thischapterprovidesyouwithsomebasictheoryaboutsome
ofthekeysettingsavailable.
WhatisTVG?
TVGmeansTimeV ariedGain.Asechoeswillbeweaker
whenthedistancetothemincrease,thesonarwillautomatically
amplifydistantechoesmorethancloseechoes.Inpractice,the
gainwillincreaseinproportionwithhowlongthesonarmust
waitfortheechoes.
Figure13TheTVGprinciple:Thegainattime(B)islargerthanattime(A)
A
(CD015005-003)
0
1
10 100 1000
B
C
WhenyouchoosetheTVGsettingyoucaneitherswitchitoff,or
choosea“XlogR”value.Thedifferentsettingsdeterminehow
muchgainthesonarwilluseastimeelapsesalongtheX-axis.A
highervaluefor“X”willmaketheangle(C)steeper.
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