Input amplitude as dBFS instead of Voltage

[kickbeer]

Hi everyone,

I'm having a problem to understand how a input voltage represented as dBFS unit. 1.4 V is full scale input of my ADC. From what i have just read, this full scale is same with 0 dBFS. what about input signal below full scale e.g 1.3 V or 1.2 V? What is the dBFS of this input level? I really need your help guys. Thank you in advanced

 

[erikl]

1.4 V is full scale input of my ADC.

Your dBFS value = 20*log(voltage/dbFS-voltage) ,
i.e. below 1.4V always negative:
voltage dBFS value
1.3V -0.64 dbFS
1.2V -1.34 dbFS
0.7V -6.02 dbFS
140mV -20 dBFS
100mV -22.9 dBFS