Test signals Dirac pulse Heaviside function Harmonic oscillation       In order to determine a system's behaviour experimentally test input signals are required that suffice the conditions of Duhamel's convolution integral. As the convolution integral describes the response to infinitely short signals the d- or Dirac-function is suitable as test signal. The Dirac pulse can be realized only approximately. Instead of it the heaviside function that corresponds to the integral of the Dirac-function may be used. Harmonic oscillations are to be used to obtain the system's response to harmonic input signals that can be obtained from arbitrary shapes by means of Fourier- or Laplace-transformation.     Top : Resources : Methods : Test signals