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457420/A

AdjustingtheTVG(TimeVariableGain)setting

Whenanacousticpulseissentthroughthewater,itwillgraduallyloseitsenergy.The

greaterthedistancebetweenthetransducerandthetarget(s),thegreaterthelossofenergy.

TVG(TimeVariableGain)compensatesforthelossofacousticenergyduetogeometric

spreadandabsorption.

Context

TheTVG(TimeV aribleGain)compensationisdesignedtocounteractthenatural

phenomenaofgeometricspreadandabsorptionloss.IntheST90,theTVGcompensationis

madeusingdigitalsignalprocessingsoftware.TheTVGcompensationisexpressedasa

logarithmiccurve.Eachcurvehasadifferentslopecreatingadifferentgaincompensation.

EachcurveisidentiedwiththeequationXlogTVG.Thecoefcient"X"isaninteger.

Typicalvaluesfor"X"are10to40.

Procedure

1Clickintheviewyouwanttoactivate.

Thesettingyouchoosewillonlybevalidfortheactiveview.Theactiveviewis

identiedwithathickerborder.

2OpentheActivemenu.

3LocatetheTVGbutton.

4Select[+]or[-]tochoosetherequestedsetting.

Relatedtopics

Controllingthegainandrangesettings,page61

Adjustingthesonarrange

Someechoesareclose,othersarefurtheraway.Itisoftennecessarytoadjusttheradiusof

thesearcharea.OntheST90,thisisreferredtoasrange.

Context

TheRangesettingdeneshow"far"youwishtheST90todetectechoes.Inotherwords,you

specifythehorizontalorverticaldistancefromthevesseltotheouteredgeofthesearcharea.

Operatingprocedures

Simrad ST90 User Manual

Other manuals for Simrad ST90