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SR1 Operation Manual 160
© 2014 Stanford Research Systems
The X-axis for this measurement is simply the harmonic number.
Using the THD Analyzer with the Time Domain Detector
The THD analyzer can be used together with the Time Domain Detector to make the most precise THD
measurements possible. Normally the selected input converter's range must be set large enough to not
overload on the the fundamental of the input signal. When using the TDD as an input to the THD
Analyzer, the analog notch filter and post filter gain eliminate the fundamental and amplify the remaining
distortion products so that the full range of the input converter can be applied to harmonics rather than
the fundamental.
To use the THD analyzer with the Time Domain Detector, select the type of one of the analyzers, say A0
to be TDD. Set the input converter of the TDD to Hi-Bandwdith and set the measurement type of the TDD
to THD+N in order to enable the notch filter. Set the type of the A1 analyzer to be THD. Set the input of
the THD analyzer to "Other Analyzer." The THD will now use as its input the notch filtered signal from
the TDD.
When using the THD analyzer in combination with the TDD to measure low levels of THD+N
be sure the TDD is set to the Hi-Bandwidth converter. Only the Hi-Bandwidth converter signal
chain employs the analog notch filter and and analog post-filter gain that enables making the
most sensitive THD measurements.