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9
8 HAMEG INSTRUMENTS
| HMO3000 SERIES
Frequency Analysis
FFT functionality
FFT functionality
Due to the outstanding FFT functionality of the HMO series oscilloscopes signals can also be analysed in
the frequency domain with up to 65,536 points. Additional practical tools such as cursor measurement as
well as peak-detect-functions are also available. They allow engineers to complete their analysis significantly
faster, also in the frequency domain.
Figure 5
Easy analysis in frequency domain
Quite often the distortion of input signals cannot be
detected with the naked eye. For instance, the sine
wave signal displayed in figure 1 appears to be
undistorted. Only the frequency spectrum (figure 2)
- available with just one touch of a button - clearly
displays additional harmonics that occur as
harmonic oscillations for multiples of the basic
frequency.
For non-periodic input signals most instruments
offer the option to trigger the spectrum at just the
right moment to then check it in “STOP” mode
at a later time. However, at that point, many
oscilloscopes with FFT functionality calculate the
spectrum only once and store the result in the
memory. The base time signal will no longer be used
for the calculation. Consequently, an investigation
of all parts of the signal will no longer be possible.
HMO series oscilloscopes work differently: Since
FFT is also active for previously stored signals, it is
possible to subsequently analyze any sections of
those signals captured in single shot mode or stop
mode with an adjustable window width. Figure 3
shows a sine burst signal in the time domain.
Pushing the FFT button will switch the oscilloscope
into the frequency domain. Users can choose
between various measurement windows like the
„rectangular“ type that has been used in figure 4.
Although this window type captures frequencies at
a high degree of accuracy, it is also accompanied
by more noise. In order to suppress this disturbing
interference users can for instance choose the
Hanning window. The impact on the spectrum is
visible in figure 5 (see device screen).
Figure 1: A sinusoid signal that at first sight appears undistorted
Figure 2: The frequency spectrum exposes the signal distortion
Figure 3
Figure 4
