72 Chapter2
Making Measurements
Example 4: Harmonic Distortion
An Alternative Harmonic Measurement Method:
Procedure B
This method is somewhat longer, but because each signal is measured
in a narrower span and resolution bandwidth, the signal-to-noise ratio
is improved, making the results more accurate.
1. Using the present setup, clear the markers from the screen by
pressing
MKR, MARKERS OFF. Notice that when MARKERS OFF or
HOLD is pressed, the display expands to the full size of the screen, for
easier viewing.
Measure the 1 MHz fundamental
1. Reduce the frequency span:
a. Press
PEAK SEARCH, which activates a marker on the
highest-level signal on-screen.
b. Reduce the frequency span to 1 MHz by pressing SPAN, SPAN
ZOOM.
c. Enter 1 MHz. The span zoom function lets you quickly "zoom" to a
narrower frequency span without losing the signal from the
screen (because signal track is activated).
d. After the frequency span is reduced, turn off the signal-track
function by pressing
MKR, and setting SIG TRK ON OFF to OFF.
2. Set the center-frequency step-size to the frequency of the
fundamental:
a. Press
MKR →, MARKER → CF STEP
3. For better amplitude accuracy, move the signal to the top of the
graticule:
a. Press
MARKER → REF LVL. The resulting display should resemble
Figure 2-19 on page 73.
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