4.Advanced User Guidebook
31
signal into its frequency components mathematically (the record length should be
10K or above). The final frequency contains 4096 points ranging from 0Hz to
Nyquist frequency.
Taking the FFT operation for example, the operation steps are as follows:
1. Press the
Math
button to display the math menu in the bottom.
2. Select
FFT
in the bottom menu.
3. In the right menu, select
Source
as
CH1
.
4. In the right menu, select
Window
. In the left menu, turn the
M
knob to select
the proper window type.
5. In the right menu, select
Format
. In the left menu, turn the
M
knob to select
amplitude unit (
V RMS
,
Decibels
) or phase unit (
Radian
,
Degrees
).
6. Select
Hori (Hz)
in the right menu; select repeatedly to make the
symbol in
front of the horizontal position value (the upper one), turn the
M
knob to adjust
the horizontal position of FFT waveform; then select to make the
symbol in
front of the time base value below, turn the
M
knob to adjust the time base of
FFT waveform.
7. Select
Vertical
in the right menu; do the same operations as above to set the
vertical position and vertical division.
To select the FFT window
■ There are 6 FFT windows. Each one has trade-offs between frequency
resolution and magnitude accuracy. What you want to measure and your source
signal characteristics help you to determine which window to use. Use the
following guidelines to select the best window.
Type
Characteristics
Window
Hamming
Better solution for magnitude than Rectangle,
and good for frequency as well. It has slightly
better frequency resolution than Hanning.
Recommend to use for:
⚫
Sine, periodic and narrow band random
noise.
⚫
Transients or bursts where the signal levels
before and after the event are significantly
different.
