With these plots, the change in the strength of the signal over time can clearly be seen. You are most likely familiar with looking at signals on an oscilloscope image, which plots the magnitude of the signal on the y-axis (vertical) and the time on the x-axis (horizontal). This instrument is also referred to as Spectrum within WaveForms. This guide explains the use of WaveForms' Spectrum Analyzer instrument. Spectrum Analyzers are used to view captured analog signals in the frequency domain. USB Scopes, Analyzers and Signal Generators.