Stanford Research Systems SR780, Operating Manual And Programming Reference

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Octave Frequency Menu 4-13
SR780 Network Signal Analyzer
1/1 Octave: [125 mHz ..]
1/3 Octave: [100 mHz ..]
1/12 Octave: [100 mHz ..]
The exact band center frequencies are calculated according to the ANSI standard. The
displayed frequencies are the ANSI nominal center frequencies.
The measurement may span 1 to 11 octaves. Decreasing the Lowest Band will also
decrease the Highest Band if necessary to keep the measurement span at 11 octaves.
The two displays can have different Lowest Bands. This entry field can be linked to both
displays using the [Link] key. Linking is only allowed if both displays have the same
Octave Resolution.
Command: OLOB (?) d {, f}
Octave Resolution
Select the Octave Resolution (number of bands per octave) for the active display [Full,
Third, Twelfth].
Full octave band centers are calculated by multiplying or dividing 1000 Hz by 2.
Third octave band centers are calculated by multiplying or dividing 1000 Hz by 2
1/3
or
1.2599.
Twelfth octave band centers are calculated by multiplying or dividing 1000 Hz by 2
1/12
or
1.0595.
The exact band center frequencies are calculated according to the ANSI standard. The
displayed frequencies are sometimes rounded to even values for a simpler display. The
filter shapes are third-order Butterworth with full, 1/3 or 1/12 octave bandwidth.
Changing the Octave Resolution will change the Lowest Band and Highest Band to
allowed bands of the new resolution.
The two displays can have different Octave Resolutions. This entry field can be linked to
both displays using the [Link] key.
Command: ORES (?) d {, i}
Octave Channels
Select the number of input channels for the octave measurement. The number of Octave
Channels affects the Measurements of both displays.
If 2 Octave Channels are selected, then both inputs may be analyzed. The Measurements
of both displays are independent. The Highest Band for all Octave Resolutions is
decreased by 2 in this case.