Aiming at the intermittent and atypical sampling faults of the data acquisition system, a method is proposed based on sinusoidal excitation, introducing a fault-free expansion curve as the reference object, and using the stable measurement curve segment between different fault segment points and the corresponding expansion curve segment. The delay time difference is determined, and the fault recovery time is determined. Finally, the fault recovery time of each fault segment and the time interval of different fault segments are used for fault identification and characterization. The identification analysis and characterization results on the atypical fault curves actually obtained that verify the practicability and feasibility of the method described in this article.