Relationship between oscilloscope and spectrum analyzer amplitude
This note explains the relationship between oscilloscope and spectrum analyzer amplitude.
Table of Contents
Application
Both oscilloscopes and spectrum analyzers measure electrical signals.
The oscilloscope measurement results are displayed on the screen as horizontal axis: time, vertical axis: amplitude.
On the other hand, the measurement result of the spectrum analyzer is displayed on the screen as horizontal axis: frequency, vertical axis: amplitude.
This note describes the relationship between the amplitude of a sine wave signal measured with an oscilloscope and a spectrum analyzer.
The graph above shows the waveform (blue line) when a sine wave signal with a maximum value of 1 mV (Peaktopeak
= 2 mV) is measured with an oscilloscope.
When this signal is measured with a spectrum analyzer, the amplitude is displayed as an rms value and the sine wave
(rms value) = (maximum value) ÷ √ 2, so it is about 0.707mV.
The notation in logarithmic units, decibels (dB), is often used in spectrum analyzers, so in that case, 0.707mV becomes
20 * log (0.707mV) = about 3dBmV = about 63dBV = about 57dBμV .
(Conversion from dBmV to dBV is minus 60 dB, and conversion from dBmV to dBμV is plus 60 dB.)
Also, considering the impedance at 50Ω, 0.707mV is about 1 × 105 mW, and 10 * log (1 × 105 mW) = 50dBm.
These relationships are summarized below.
Oscilloscope  Spectrum analyzer  

MAX  Peaktopeak  Voltage  Power (impedance 50Ω)  
1mV  2mV  0.707mV  －3dBmV  －63dBV  57dBμV  1×105 mW  －50dBm 
System configuration］
Handheld signal analyzer MSA500 series 
Handheld spectrum analyzer MSA400 series 
Products introduction
Handheld signal analyzer MSA500 series
With Fast Fourier Transform (FFT) and conventional sweep systems, each strong point of both systems is usable.

Handheld Signal Analyzer MSA538
The most popular model of the MSA500 series.
Measurement frequency : 20kHz to 3.3GHz 
Handheld Signal Analyzer MSA538TG
Builtin TG from 5MHz to 3.3GHz
Measurement frequency : 20kHz to 3.3GHz 
Handheld Signal Analyzer MSA538E
This is a model in which EMI measurement function is added to MSA538.
Measurement frequency : 20kHz to 3.3GHz 
Handheld Signal Analyzer MSA558E
This is a model in which EMI measurement function is added to MSA558.
Measurement frequency : 20kHz to 8.5GHz 
Handheld Signal Analyzer MSA558
Almost all of the applications of wireless communication systems are covered.
Measurement frequency : 20kHz to 8.5GHz
Handheld Spectrum Analyzer MSA400 Series
MSA300 series was extremely upgraded to MSA400 series.This product has large color display.

Handheld Spectrum Analyzer MSA438
The most popular model in MSA 400 series.
Measurement frequency : 50kHz to 3.3GHz 
Handheld Spectrum Analyzer MSA458
Almost all of the applications of wireless communication systems are covered.
Measurement frequency : 50kHz to 8.5GHz 
Handheld Spectrum Analyzer MSA438TG
Builtin TG from 5MHz to 3.3GHz.
Measurement frequency : 50kHz to 3.3GHz 
Handheld Spectrum Analyzer MSA438E
This is a model in which EMI measurement function is added to MSA438.
Measurement frequency : 50kHz to 3.3GHz