Math Fft; Setting Up The Time-Domain Waveform - Tektronix TDS2000C series User Manual

Math FFT

Setting Up the Time-Domain Waveform

TDS2000C and TDS1000C-EDU Series Oscilloscope User Manual
This chapter contains detailed information on how to use the Math FFT (Fast
Fourier Transform). You can use the FFT Math mode to convert a time-domain
(YT) signal into its frequency components (spectrum). You can use the Math FFT
mode for the following types of analysis:
Analyze harmonics in power lines
Measure harmonic content and distortion in systems
Characterize noise in DC power supplies
Test impulse response of filters and systems
Analyze vibration
To use the Math FFT mode, you need to perform the following tasks:
Set up the source (time-domain) waveform
Display the FFT spectrum
Select a type of FFT window
Adjust the sample rate to display the fundamental frequency and harmonics
without aliasing
Use zoom controls to magnify the spectrum
Use cursors to measure the spectrum
Before you use FFT mode, you need to set up the time-domain (YT) waveform.
To do so, follow these steps:
1. Push AutoSet to display a YT waveform.
2. Turn the vertical Position knob to move the YT waveform to the center
vertically (zero divisions).
This ensures that the FFT will show a true DC value.
3. Turn the Horizontal Position knob to position the part of the YT waveform
that you want to analyze in the center eight divisions of the screen.
The oscilloscope calculates the FFT spectrum using the center 2048 points of
the time-domain waveform.
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