Agilent Technologies 33220A User Manual page 337

7
Chapter 7 Tutorial
Attributes of AC Signals
Note. If an average-reading voltmeter is used to measure the "DC
voltage" of a waveform, the reading may not agree with the DC Offset
setting of the function generator. This is because the waveform may have
a non-zero average value that would be added to the DC Offset.
You may occasionally see ac levels specified in "decibels relative to
1 milliwatt" (dBm). Since dBm represents a power level, you will need to
know the signal's RMS voltage and the load resistance in order to make
the calculation.
dBm = 10 x log (P / 0.001)
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For a sine wave into a 50Ω load, the following table relates dBm to voltage.
dBm RMS Voltage
+23.98 dBm 3.54 Vrms
+13.01 dBm 1.00 Vrms
+10.00 dBm 707 mVrms
+6.99 dBm 500 mVrms
0.00 dBm 224 mVrms
-6.99 dBm 100 mVrms
-10.00 dBm 70.7 mVrms
-36.02 dBm 3.54 mVrms
For 75Ω or 600Ω loads, use the following conversions.
dBm (75Ω) = dBm (50Ω) – 1.76
dBm (600Ω) = dBm (50Ω) – 10.79
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where P = V / R
RMS
Peak-to-Peak Voltage
10.00 Vpp
2.828 Vpp
2.000 Vpp
1.414 Vpp
632 mVpp
283 mVpp
200 mVpp
10.0 mVpp
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