User Manual

Analyzing a wave
form
8. Push the Horizontal Scale side-menu
button and use the Multipurp ose knob
to set the hori
zontal scale (frequency per
major graticule division) value. Use this
to expand or contract the FFT waveform
to show more o
r less detail. The FFT
waveform expands around the center
cursor.
9. Push the Cur
sors front-panel button and
use the cursors to take measurements.
FFT tips
You can only display FFT waveforms for 2000 and 20K record length waveforms.
Use the Vertical Position knob of the source channel to change the vertical position of the FFT waveform.
Use the Vertical Scale knob of the source channel to change the vertical size of the FFT waveform.
Use cursors to measure frequencies and relative signal levels.
Input signals that have a DC component or offset can cause incorrect FFT waveform component magnitude values. To
minimize the DC component, use AC Coupling on the input signal.
To reduce random noise and aliased components (See page 63.) in repetitive or single-shot events, set the oscilloscope
acquisition m ode to average over 16 or more samples. Average mode attenuates signals not synchronized with the
trigger.
Do not use the Average acquisition mode if the source signal contains frequencies of interest that are not synchronized
with the trigger rate.
For transient (impulse, one-shot) signals, set the oscilloscope trigger conditions so that the transient pulse waveform is
centered in the waveform record.
TBS2000 Series User Manual 61