Measurements 14
Keysight InfiniiVision HD3-Series Oscilloscopes User's Guide 207
Total Harmonic Distortion (THD) measures the power contained in the bands
surrounding each harmonic and compares it to the power in the band surrounding
the fundamental frequency. The width of the bands measured is the same for the
fundamental frequency and each harmonic. That width is 1/2 of the fundamental
frequency.
You can either enter the fundamental frequency as a measurement parameter and
have the fundamental frequency and harmonics be tracked manually, or you can
allow the fundamental frequency and harmonics to be tracked automatically,
where the highest peak is assumed to be the fundamental frequency.
When this measurement is tracked with markers, the markers show the band
surrounding the fundamental frequency that is being measured (at ±1/4 of the
fundamental frequency).
Measurement Thresholds
Setting measurement thresholds defines the vertical levels where measurements
will be taken on an analog channel or math waveform.
1 From the menu, choose Measure > Measurements....
2 In the Measurements dialog box, select the Settings tab.
3 Select Thresholds....
4 In the Measurement Thresholds dialog box:
• There are tabs for Channels, Math, and Reference waveforms.
Each analog channel, math function, and reference waveform can be
assigned unique threshold values.
Changing default thresholds may change measurement results
The default lower, middle, and upper threshold values are 10%, 50%, and 90% of the value
between Top and Base. Changing these threshold definitions from the default values may
change the returned measurement results for Average, Delay, Duty Cycle, Fall Time,
Frequency, Overshoot, Period, Phase, Preshoot, Rise Time, +Width, and -Width.
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