I am doing some measurement involving EMG signals (but it could also have been sound, the suggestion would have been the same).
For the output signal generator, the sweep can either be up or down in a fixed steps. It would be much more practical to have a log scale.
Imagin testing a loudspeaker, you step the frequencies through: 10, 20, 50,100, 200, 500,..... 20000 Hz. Typically between 3 and 10 steps per decade.
For ps6, it would be practical to specify:
1) start frequency
2) stop frequency
3) No of steps.