Tektronix DPO2304SX, Printable Help, Page: 287 / 920

Using spectral analysis
Spectral analysis overview
You can use math waveforms to perform FFT (Fast Fourier Transform) measurements with the instrument. The FFT process
mathematically converts the standard time-domain signal (repetitive or single-shot acquisition) into its frequency components,
providing spectral analysis capabilities.
The ability to quickly look at signal frequency components and spectrum shape is a powerful research and analysis tool. FFT is
an excellent troubleshooting aid for the following:
■ Testing the impulse response of filters and systems
■ Measuring harmonic content and distortion in systems
■ Identifying and locating noise and interference sources
■ Analyzing vibration
■ Analyzing harmonics in 50 and 60 Hz power lines
■ Continue
Spectral analysis features
You can display an FFT waveform on any actively acquired signal (periodic or single-shot), the last acquired signal, or any signal
stored in reference memory.
FFT windows. The instrument allows you to match the optimum window to the signal you are analyzing.
■
The Rectangular window is best for nonperiodic events such as transients, pulses, and single-sequence acquisitions.
■
The Hamming, Hanning, and Blackman-Harris windows are better for periodic signals.
■
The Kaiser Bessel window has less spectral leakage than the Hanning, Hamming, or Rectangular windows.
■
The Gaussian window provides optimal localization in both the time and frequency domain.
■
The Flattop2 window is good for high accuracy magnitude measurements for signals that do not require narrow resolution
bandwidth.
■
The Tek Exponential window is useful for impulse response testing.
Vertical scales. The FFT vertical graticule can be set to either dB or Linear RMS.
■
A dB scale is useful when the frequency component magnitudes cover a wide dynamic range, letting you show both lesser
and greater magnitude frequency components on the same display.
■
A Linear scale is useful when the frequency component magnitudes are all close in value, enabling direct comparison of
their magnitudes.
Spectral and Time-Domain displays. Time signals and FFT waveforms can be shown together on the display. The time signal
highlights the problem; the FFT waveform helps you determine the cause of the problem.
■
Continue
■
Previous
FFT process
The FFT process mathematically converts the standard time-domain signal (repetitive or single-shot acquisition) into its
frequency components.
The FFT function processes the waveform record and displays the FFT frequency domain record, which contains the input signal
frequency components from DC (0 Hz) to ½ the sample frequency (also called the Nyquist frequency).
Math setups
DPO70000SX, MSO/DPO70000DX, MSO/DPO70000C, DPO7000C, and MSO/DPO5000B Series 255