User manual
37
Analysis
Afterwards, a new equation MA2 will be entered and ad-
justed. The result of the equation calculation „CURRENT“
and channel CH2 will be multiplied which will be yielded
to a power curve. The equation MA2 can be named „PO-
WER“ using the soft menu key LABEL. At last, a 3rd equa-
tion MA3 will be added to the set of formulas which will
bedenedastheintegraloftheequation„POWER“.The
equation MA3 can be named „ENERGY“ using the soft
menu key LABEL.
Now,alldenitionswillbecompletedandtheresultscan
be displayed and analysed. The math analysis can be per-
formed with cursor or automatic measurement functions.
All measurement results will be correctly shown and sca-
led with correct units: Ampere, Watt, Joule.
9.2 Frequency Analysis (FFT)
In general, the FFT in an oscilloscope works differently than
in a spectrum analyzer and is affected not only by the time
base setting, but also by the available number of used
a
cq
uired data points when calculating the FFT. The
R&S®HMO1002 allows you to include up to 65k point in the
FFT.
The FFT menu in the ANALYZE section allows a quick Fou-
rier transformation which displays the frequency spect-
rum of the measured signal. The changed display allows
you to determine the most frequent frequencies in the sig-
nal and the corresponding amplitude. Once the FFT key
was pressed, the screen will be divided into two graticu-
les. The upper left of the display shows information about
the settings in the time range, the area between the upper
and the lower window shows details about zoom and po-
sition, and the section below the large FFT display window
indicates the settings (Span and Center) in the frequency
range. The lower FFT display window will be outlined in
white when the FFT is activated. This means that the large
knob in the time range section is used to select the span.
ThespanisspeciedintheunitHz(Hertz)andidenties
the width of the shown frequency range. The span posi-
The FFT is not suitable for the analysis of very slow signals (Hz-
range); this type of analysis requires a classic oscilloscope mode.
Fig. 9.7: FFT illustration
tion can be determined by selecting the center value. You
may use the horizontal encoder X Position for this purpose.
The shown frequency range ranges from (Center - Span/2)
to (Center + Span/2).
The soft menu key MODE allows you to choose from the
following display types:
❙ REFRESH:
This mode calculates and displays the FFT without
additional evaluation or editing of the captured data. The
new input data is captured, displayed and overwrites
previously stored and displayed values.
❙ ENVELOPE:
IntheEnvelopemode,themaximumdeectionsofall
spectra will be stored separately in addition to the current
spectrum and will be updated with each new spectrum.
These maximum values will be displayed with the input
data and create an envelope curve. The spectrum is
located within the envelope limits. This forms an area or a
sleeve including all occurrences of FFT signal values.
With each signal parameter change the envelope curve
will be reset.
❙ AVERAGE:
This mode calculates the mean value from several
spectra. It is applicable for noise reduction. The soft
menu key #AVERAGES allows you to select the number
of spectra used to calculate the mean value by setting
the universal knob in the power of 2 from 2 to 512.
The menu entry POINTS allows you to select the maximum
number of capture points to be included in the calculation
by using the universal knob in the CURSOR/MENU section.
The possible settings are 2048, 4096, 8192, 16384, 32768,
65536 points. The soft menu WINDOWS allows you to
improve the FFT display in case of irregularities at the
margins of the measurement interval. Irregularities are
calculated as a leap by a computing algorithm and interfere
with the measurement result. In the event of a bell-shaped
window function, the margins with lower values are
The minimum increment depends on the time base. The greater the
time base, the smaller the span. Another important element for the
FFT is the setting “Max. Sampling Rate” in the ACQUIRE menu.
Fig. 9.8: Advanced FFT menu