A signal is attached to Channel-1 of an Agilent 35670A Dynamic Signal Analyzer. The unit of the signal measured by the analyzer is as follows:

Time Capture (time domain): Volt (V)

Linear Spectrum (frequency domain): Volt-RMS (Vrms)

Power Spectrum (frequency domain): Volt-RMS (Vrms)

However, some online articles, for example the following:

http://zone.ni.com/reference/en-XX/help ... _spectrum/

http://www.onosokki.co.jp/English/hp_e/ ... _term5.htm

... show that for a voltage signal, the unit of the power spectrum of the signal is Volt-RMS squared (Vrms^2).

Which one is correct?

Thanks.

Time Capture (time domain): Volt (V)

Linear Spectrum (frequency domain): Volt-RMS (Vrms)

Power Spectrum (frequency domain): Volt-RMS (Vrms)

However, some online articles, for example the following:

http://zone.ni.com/reference/en-XX/help ... _spectrum/

http://www.onosokki.co.jp/English/hp_e/ ... _term5.htm

... show that for a voltage signal, the unit of the power spectrum of the signal is Volt-RMS squared (Vrms^2).

Which one is correct?

Thanks.

Now, I read on trace A, a value of 1.48528 V which is approximately 1.5 V. This is the amplitude of the source signal we were outputting.

Linear spectrum in trace B shows 1.06069 Vrms. The way we compute Vrms is Vpk * .707. So, in this case, it should be close to 1.5 V * .707 = 1.0605 Vrms. Now, you can view the linear spectrum in units of Vpk by going to (first activate just trace B) Trac Coord > Y units > Amplitude PK. When I do that I get 1.50004 V displayed which is close to the source level output of 1.5 Vpk.

Power spectrum in trace C shows 1.06069 Vrms. The way we compute Vrms is Vpk * .707. So, in this case, it should be close to 1.5 V * .707 = 1.0605 Vrms. Now, you can view the power spectrum in units of Vpk^2 by going to (first activate just trace C) Trac Coord > Y units > Amplitude PK and VOLT^2. When I do that I get 2.25013 Vpk ^2 displayed which is close to the source level output of (1.5 Vpk )^2 = 2.25 Vpk^2. For units of Vrms ^2, the conversion factor is (.707)^2. So, a 2.25013 Vpk^2 changes to 1.12507 Vrms^2 which is nothing but 2.25013 * (.707)^2.

Hope this clarifies some!