Characterises the transient response of a linear system in the frequency range. It is independent on the type of system excitation, i.e. it is irrelevant whether a system is excited by a periodic or transient input signal.
If, on a linear system, a harmonic oscillation is provided as the input signal, the is also a harmonic oscillation that has, however, a different amplitude and a different phase position (Figure F 34).
Consequently the frequency response of a continuously adjustable valve according to DIN 24 311 is the ratio of the output signal (e.g. flow rate, pressure) to the sinusoidal input signal (e.g. input current) in the steady-state, represented as function of the angular frequency ω or the frequency f.
To describe the frequency response normally the frequency at an amplitude ratio of -3 dB and a phase-frequency response of -45° or -90° is selected.
Figure F 34: Frequency response characteristics