Tektronix TBS2072, Руководство пользователя

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Analyzing a waveform
An example of using a math waveform is
to calculate instantaneous power (current
times voltage) by multiplying a voltage
waveform and a current waveform.
Math waveform tips
Math waveforms get their horizontal scale and position from the sources channels. Adjusting these controls for the
source waveforms also adjusts the math waveform.
Adding or subtracting waveforms with different units sets the math waveform units to “?”.
You can take automatic measurements on math waveforms similarly as on channel waveforms. Just select the Math
side menu in the Measure screen and select the measurements to apply.
You can save a math waveform to a reference memory or to a fi le on a USB drive. You can also recall (load) math
waveforms into reference memory. (See page 72, Recalling waveform data .)
You can zoom in on math waveforms using the Navigation controls ( Zoom button and Multipurpose knob).
Using FFT to see signal frequency information
There are many signals that have some sort of distortion or unwanted characteristics. Sometimes these distortions do not
affect how that signal works in the circuit. But often system clock pulses, signals induced from a nearby printed circuit path,
or noise from a power supply or other source can affect a signal and prevent it from operating correctly. The FFT function is a
powerful tool to help you
fi nd the frequencies of unwanted signals that are embedded in your main signal.
The FFT function uses Fast Fourier Transformation (FFT) mathematical calculations on the waveform data to determine the
component frequencies in the signal. The resulting waveform shows a series of ‘spikes’ along a horizontal axis, where each
spike represents a frequency component of the waveform and its amplitude. In other words, an FFT is a basic spectrum
analyzer function to analyze frequency components of a waveform.
1. Acquire and display several cycles of the
waveform.
NOTE. You can only display FFT waveforms for
2000 and 20K point record length waveforms.
2. Push F ( FFT ) button.
TBS2000 Series User Manual 59