Simrad EK15 - TVG Function

Functionsanddialogboxes
TVGfunction
TheTVGfunctionisactivatedbyclickingtheTVGbuttonontheActivemenu.
Purpose
TheTVG(TimeVariableGain)functionallowsyoutocompensatethereceiveddata
forlossduetogeometricspread.
Description
TVGmeansTimeVariedGain.
ThewholeideawithTVGisthatechoesfromshshall
havethesameecholevel(colour)independentoftheir
depths.
TheEK15hasaTVGrangedownto15000meters,
whichforallpracticalpurposesisunlimited.The
EK15doesnothaveaTVGcompensatedreceiverlikemostotherechosounders.Inthe
EK15theTVGismadeinsoftwareaftertheechoesfromthereceiver(s)havebeen
convertedtodigitalformat.Inordertomakethisworkthereceivermusthavevery
largedynamicrange.
TheTimeV ariedGain(TVG)functionalitycompensatesforpropagationattenuationof
thesoundwavesreectedfromatargetinthewater.Basicallyitwillequalizeecho
presentationthroughoutthewatercolumnsothattargetsofthesamesizeappearinthe
samedensityindependentofrangeordepth.
TheselectionmadeusingtheTVGbuttonisthesameasontheEchogramtabinthe
Echogramdialogbox.
TheTVGfunctionisdescribedinmoredetailintheechosoundertheorychapter.
TheTVG(TimeV ariableGain)controlsthegaininthesignalamplier.Thegainis
weakestjustaftertheping,andincreasesinaccordancewithtime(andthereforerange)
Theconstant[x]inthe[x]LogRequationwillshapetheTVGcurve.
Parameters
1TVG
ThefollowingTVGsettingsareavailable:
aPower(NoTVG)
TVGgainisnotimplemented.Thissettingishardlyeverused.
bSchool(20logTVG)
Thisgainsettingoffersweakeramplicationclosetothebottom.Ithasbeen
designedtoprovidethebestechoesforschools.Thephysicalsizeofaschool
allowsyoutodetectitevenwithreducedgain.
351718/C
215