edwaveisy=Acos(πLλ)cos(πft)()WhereAistheamplitudeofacousticwave,fisthefrequency,Listhedistancefromtheliquidsurfacetothetopoftube,λisthewavelengthoftheacousticwave.Listhelevelheightneededtobecalculated.WhenλandLsatisfytherelationbelowL=nλ,n=,,...()theamplitudeofthesynthesizedwavewillreachthepeak.Itswavelengthisλ=c/f,andthenL=nc(f)()Wherecisthesoundvelocity,fistheacousticfrequencyandTisthecentigrade.Figure.LevelgaugewithsingletubeFigure.LevelgaugewithdoubletubesFigure.WaveformgraphFigure.showsasetupoflevelgaugewithsingletube.Whenthetransmitteremitssoundwavesverticaltothefluidsurfacewhosefrequencieschangewithuniformspeed,themicrophonereceivestheresonanceandsendsthesignaltothecontroller.Figure.showsthesynthesizedsinewaveswhicharechangedatequaltimeintervalswhensinewavefrequencieschangefromHztoHz.Heretheverticalaxisden。
例如{f(k)/n(k)