Method for accurate fault diagnosis in an inkjet print head

In a method for identifying of and distinguishing between at least two different predetermined disturbance states in an inkjet print head, the method comprises providing a disturbance identification input signal; applying the disturbance identification input signal to an actuator, the actuator being part of an ejection unit of an inkjet print head; receiving a residual pressure wave output signal; and analyzing the residual pressure wave output signal. The step of analyzing comprises designing and providing a respective mathematical analysis operator for each identifiable disturbance state; executing each respective mathematical analysis operator using the received residual pressure wave output signal as an input for each respective mathematical analysis operator; comparing an output of each respective mathematical analysis operator to a respective predetermined output reference; deciding for each predetermined disturbance state whether the disturbance state is present, wherein it is decided that a corresponding disturbance state is present, if an output of a respective mathematical analysis operator corresponds to the respective predetermined output reference; and it is decided that a corresponding disturbance is not present, if an output of a respective mathematical analysis operator does not correspond to the respective predetermined output reference