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IfyouchangetheunitstodBVrms,herearethevalues:
Whenthesettingsare20dBVrms/divandthereferenceismovedtoone
divisiondownfromthetopoftheFFTdisplay:
Divisionsdownfromtop
ofFFTscreen
dBVrmsfromposition
marker
Valueattopofthat
division
0 +10dBVrms 3.16Vrms
1 0dBVrms 1Vrms(attheposition
marker)
2‐10dBVrms .316Vrms
3‐20dBVrms .1Vrms
4‐30dBVrms .0316 Vrms
5‐40dBVrms .01 Vrms
6‐50dBVrms .00316mVrms
7‐60dBVrms .001 mVrms
8‐70dBVrms .000316mVrms
Tounderstandthisfully,theformulatoderivethedBVrmsvalueisasfollows:
dBVrms=20*log(Vrms/VREF)
whereVREFinthiscaseis1Vrms,soitcanbesimplifiedto:
dBVrms=20*log(Vrms)
Consequently,whenlookingataspotonthescreenthatisknownto
beX
dBVrmstheactualVrmsvalueexpressedbysignalatthatlocationis:
Vrms=10^(X/20)
Forexample,‐20dBVrms=10^‐1=0.1Vrms