Sanwa U-50D Operator's Manual page 26

Voltage - 20 log,,, ? 2
Current - 20 log,o-j2
Power - 10 logio— —■ -
They are decibels.
output by ratio independently from each other, and can
not be taken as comparison values. For comparison, there
must be a reference value.
As a rule, OdB is set at a voltage when 0.001 watt is dissi­
pated across a 600-ohm line, while voltage (E) is related
to decibel as follows :
!' L E — \/Px Z.j
Z, u
{Zo: Line impedance)
Therefore, zero reference level is established at approxi­
mately 0.775 volt.
Though a meter does not read power level directly, if the
line impedance is uniform, it can be known by the
voltage because voltage and power are proportionately
related. If the line impedance is converted to a 600-ohm
reference level, the dB scale of the meter directly reads
decibel.
hi
° Input (E,) j Circuit j O u tp u t;'(E ^
Po
Pi
But they only express input and
i/0'.bOT- OiKi'- 0. 77-15
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