External Sweeps with APx

Created on 2009-03-12 16:57:00

Question:

I would like to characterize a play-only device with my APx audio analyzer. Can I make my own sweep stimulus signals to load into my device?

Answer:

APx has two measurements which support external (aka open-loop) sweep  signals: Measurement Recorder and Stepped Frequency Sweep.

The Measurement Recorder provides readings for level, phase, THD+N (ratio & level), DC level, frequency, and more. Using Measurement Recorder, you can measure any arbitrary sweep, but all the measurement graphs will have time on the x-axis. That is, it will record level vs. time, phase vs. time, THD+N vs. time, DC level vs. time, and frequency vs. time. If you wish to, for example, view level vs. frequency, you can export the data to Microsoft Excel and plot level vs. frequency there.

The Stepped Frequency Sweep measurement provides readings for level, relative level, deviation, phase, THD+N, SINAD, and distortion products. The measurement needs to be told what frequencies to expect, either from a list of predetermined sweeps, or from a user-defined table. You can also generate a user-defined sweep .wav file from within the measurement. The Output Connector in Signal Path Setup should be set to “None (External).” Signals can also be found on the APx CD1, DVD1, and BD1 discs, or generated quickly using the APx Waveform Generator Utility available in the Downloads section of ap.com.