Decibel Measurements - Chauvin Arnoux C.A 406 Mode D'emploi

Reading
To obtain the value of the voltage in V, multiply the reading on the appropriate scale by
the reading coefficient, as shown below.
V range
100mV (1)
DC
1V
3V
AC 3V (2)
10V
DC
30V
and 100V
300V
AC
1000V
(1) Position common to the 50µA DC range.
(2) Position common to the 150µA AC range.
4.2

Decibel measurements

Reminders and definitions :
The measurement of an AC voltage can be expressed in decibels (dB). The decibels is a
ratio of two quantities or levels. It is basically used to determine the output power of
amplifiers; normally the output voltage U is measured.
The reference power P
resistance of 600Ω, thus a reference voltage U
Level N, in dB, of voltage U is expressed mathematically as :
N dB = 20 log
10
Scales
Black 100
Black 100
Black 30
Red 3
Black 100
Black 30
Black 100
Black 30
Black 100
chosen as zero level in telecommunications is 1mW, with load
0
0
U
U
0
27
coefficient
Direct reading
of 0.755V AC.
Reading
in mV
x 0.01
x 0.1
x 1
x 0.1
x 1
x 1
x 10
x 10