The spectrogram measurement feature is used to monitor the power spectral density of continuous spectrums over time. It is suited to visualize and analyze time-varying spectral activity. Communication standards, based on frequency division multiple access (FDMA) and time division multiple access (TDMA) techniques, can be analyzed through a spectrogram. In the spectrogram chart, the horizontal axis shows the frequency (FFT points) and the vertical axis represents the time (duration). Each line in the chart defines a time frame. Therein, the power levels at the frequencies are drawn using a pre-defined color range. That means each color defines a certain power level. A spectrogram starts with an empty pane and the topmost line is always the latest spectrum. As the measuring advances, the pane is continuously filled with the colored power levels of the time frames. In case there is no empty line left, the eldest time frame is discarded.

A maximum level of color details should be displayed in a spectrogram. This requires an adequate, user-defined mapping of a color range to a targeted power range.