Db And Dbm Voltage Measurements; Application: Using A Reference Value Other Than Default 1.000 V Rms In Db Mode; Application: Using Voltage In A Circuit As The Reference Value In Db Mode - Fluke 183 User Manual

dB and dBm Voltage Measurements

Measurement
1
dB (185 only)
dBm (185
2
only)
1
dB readout = 20 X log (main display readout/ref), where ref = 1 V is the
default.
2
dBm readout = 10 X log (main display readout2/R), where R=600
Application: Using a Reference Value Other than Default
1.000 V RMS in dB Mode
To manually change the reference voltage in dB mode, press and hold the
yellow (shift) button to display the Setup menu. Adjust the
the value you want and press softkey
measurements will use this stored value as the reference voltage until you turn
off the meter.
Application: Using Voltage in a Circuit as the Reference
Value in dB Mode
An example of using a voltage in a circuit as the reference value is measuring
the AC voltage gain of an amplifier. Set the meter to dB mode and measure the
voltage that you want to use for the reference (the input of the amplifier). Press
to save the measured value as the reference value. Next, measure the
REL
output of the amplifier. The voltage gain of the amplifier (in dB) shows in the
upper display.
In both of these applications, the
indicate the reference is a voltage other than the default value of 1.000 VRMS.
The reference value returns to 1.000 V when you exit dB mode.
Softkey Connect Leads
dB
or dBm
(press to
toggle)
indicator shows in the upper display to
True RMS Digital Multimeters
Operating Basics
Main
Display
AC
AC
ahr08f.eps
rEF (dB)
for OK. Subsequent dB
Upper
Display
dB
dBm
e.
value to
15