The electrical characterization of single cells, cell suspensions, and tissue but also functionalized surfaces for sensing applications based on impedance spectroscopy is widely deployed and well accepted. While most applications use step sinus excitation for sweeping through the frequency range of interest, methods in the time domain with broad bandwidth excitation signals like multi sinus or chirp become increasingly prominent. The use of transient excitation like Dirac function or step function exhibits advantages for low energy applications with low hardware requirements. Especially the electric relaxation of a system after the application of a voltage or current step is comparatively simple to monitor while the generation of the stimulus does not need extensive hardware. Established models for biological objects but also for electrodes and functionalized surfaces can be calculated directly in the time domain without transformation into the frequency domain. As an example, we present an impedimetric sensor for detecting the growth of bacterial biofilms. [ABSTRACT FROM AUTHOR]