User`s guide

2 Making Measurements
Making dB Measurements
46 U1273A/U1273AX User’s Guide
Making dB Measurements
Your multimeter is capable of displaying voltage as a dB
value, either relative to 1 milliwatt (dBm) or a reference
voltage of 1 volt (dBV).
Displaying dBm values
To set the multimeter to display voltage values in dBm, first
set up your multimeter to measure voltage as shown in
Figure 2- 2 or Figure 2- 5. Probe the test points, and read the
display. Then, press until the voltage measurements are
displayed as a dBm value.
Table 2- 5 Rotary switch positions allowing dBm measurements
Legend Default function Function when is pressed
AC V AC V with LPF
AC mV AC mV with LPF
DC V
Cycles between
• AC V,
• AC+DC V, or
• DC V
DC mV
Cycles between
• AC mV,
• AC+DC mV, or
• DC mV
Exit
Dual
S
h
i
f
t
V
i
e
w
E
s
c
NOTE
A dBm measurement must use a reference impedance (resistance) to
calculate a dB value based on 1 milliwatt. The reference impedance is set
to 50 Ω by default. To select another reference value, see the “Changing
the custom dBm reference impedance” on page 115.