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SR1 Operation Manual 170
© 2014 Stanford Research Systems
The Multitone Trigger Panel
The analyzer trigger is useful in making several different types of multitone measurements. For
measurements where the SR1 generator is locally producing the stimulus signal (as opposed to a
recorded or broadcast stimulus signal), selecting the Generator Trigger option will maintain a constant
time relation between the generated signal and the received FFT frame. This calibrates the MTA's
"Frequency Response Phase" measurement which will have zero phase when a wire is connected from
the input to the output. When a device is inserted between the input and the output the phase and group
delay can be directly read off using the MTA.
For broadcast or recorded multitone stimuli the generator trigger is obviously no longer useful as the
SR1's generator no longer has any relation to the actual occurrence of the stimulus signal. Likewise,
amplitude triggers may trigger on noise and miss the multitone signal. For these situations the analyzer
provides a "validation" option which is a specialized form of analyzer trigger applicable only to the
Multitone Analyzer. The validator works by assigning a score to each received FFT based on the ratio of
the amplitudes of tone bins to non tone bins. Only received FFTs that score higher than the selected
validation criteria (Loose, normal, or tight) will be processed by the analyzer. In general it is best to use
the "tightest" validation criteria that still finds the multitone signal as it will generally produce the best
measurement results.