QA402 User Manual
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For THD and THD+N, the context menu is as follows. The Measurement Start and Stop frequency is the same
as the RMS setting. That is, you set a measurement start and stop frequency globally, and that is used for all
measurements that need a measurement start and stop specified. In the case of THD+N, the noise is computed
by measuring the spectrum from the start to stop frequency.
You can specify your preference for THD and THD+N measuremen
ts. If you select “dB”, then when you add a
THD measurement it will default to dB. Otherwise, it will default to percent.
The fundamental selection is where you tell the application how to determinate the primary frequency of
interest. That can either be specified by the Generator 1 settings, the peak as measured on the left channel or
a user-specified frequency.
The settings you have picked for Fundamental Selection will result in a small green “F” on the display as shown
below. This makes it easy to know if your fundamental has been correctly determined or not.