User manual

SimradES70
Dynamicrangeanddisplaypresentation
TheES70echosounderhasadynamicrangeof140dB.Thismeansthatthesounder
canreceivebothverystrongandveryweakechoes.Actually,theES70willdetect
echoesfromplanktontowhales,bottomonmostdepths,andpresenttheinformationfree
fromdistortion.Asacomparison,ouroldechosoundersES380andET100had-using
analogueTVG-adynamicrangecorrespondingtoapproximately65dB.
Naturally,wecannotpresentalltheseechoesonthedisplaysimultaneously,asthis
wouldcreateamessofcolours.
Figure8DynamicrangeinES70
(CD010217-001)
-25dB/W
-165dB/W
140dB
36dB
70
ColourScale
When12coloursareused,wecreate
a36dBsectionandgiveeachcolour
a3dBstrength.Everycolour(3dB)
therepresentadoubling
oftheecho
strength.With12coloursinusethis
willbea36dBcolourrangefromgrey
tobrown.Greyisusedfortheweakest
echoes,whilethestrongestechoesare
brown.Allechoesstrongerthanbrown
willstillbebrown,whileechoesweaker
thangreywillnotbeshown.
With64coloursinuse,eachcolour
representsapproximately0.5dBecho
strength.
Theoldpapersoundershadadynamic
rangeof12dBintheirprintoutsusing
the“colours”fromlightgreytoblack.
ThedynamicrangeintheES70colour
presentationisthusalotlarger;24dB
or250times.
Alongthedynamicrangewetakethe36dBsectionand“movesit”upanddownwith
thesettingsintheGainbuttonontheMainmenu.
UsetheColourScaleinformationpanetomonitorthecoloursincurrentuse.Tochange
thecolourscale,usetheColourSetupfunctionontheDisplaymenu.
Relatedtopics
•ColourScaleinformationpaneonpage137
•Gainonpage162
•ColourSetuponpage176
Bottomslopes
“Bottomslopes”isawellknownphenomenonwithechosounders.Thishappenswhen
thebottomrisessuddenly,andthestartedgeofthetransducerbeamdetectsthebottom
beforetheoppositeedge.
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